In fact, the author of RTC in his "reflections" has gone so far as to provoke heavy counter-arguments, namely, the data of the experiment of Japanese scientists on photographing the hydrogen atom, which became known on November 4, 2010. The image clearly shows the atomic shape, confirming both discreteness and roundness of atoms: “A group of scientists and specialists from the University of Tokyo for the first time in the world photographed a single hydrogen atom - the lightest and smallest of all atoms, news agencies report.
The picture was taken using one of the latest technologies - a special scanning electron microscope. With the help of this device, together with the hydrogen atom, a single vanadium atom was photographed.
The diameter of a hydrogen atom is one ten-billionth of a meter. Previously it was believed that it was almost impossible to photograph it with modern equipment. Hydrogen is the most abundant substance. Its part in the entire Universe is approximately 90%.
According to scientists, other elementary particles can be captured in the same way. “Now we can see all the atoms that make up our world,” said Professor Yuichi Ikuhara. "This is a breakthrough to new forms of production, when in the future it will be possible to make decisions at the level of individual atoms and molecules."
Hydrogen atom, conventional colors
http://prl.aps.org/abstract/PRL/v110/i21/e213001
A group of scientists from Germany, Greece, the Netherlands, USA and France took pictures of the hydrogen atom. These images, obtained with a photoionization microscope, show the electron density distribution, which completely coincides with the results of theoretical calculations. The work of the international group is presented on the pages of Physical Review Letters.
The essence of the photoionization method consists in the sequential ionization of hydrogen atoms, that is, in the detachment of an electron from them due to electromagnetic irradiation. The separated electrons are directed to the sensitive matrix through a positively charged ring, and the position of the electron at the moment of collision with the matrix reflects the position of the electron at the moment of ionization of the atom. The charged ring, which deflects electrons to the side, acts as a lens and with its help the image is magnified millions of times.
This method, described in 2004, was already used to take “photographs” of individual molecules, but physicists went further and used a photoionization microscope to study hydrogen atoms. Since the impact of one electron gives only one point, the researchers accumulated about 20 thousand individual electrons from different atoms and compiled an average image of the electron shells.
According to the laws of quantum mechanics, an electron in an atom does not have any definite position by itself. Only when an atom interacts with the external environment, an electron with some probability is manifested in a certain vicinity of the atomic nucleus: the region in which the probability of detecting an electron is maximum is called the electron shell. The new images show the differences between atoms of different energy states; scientists were able to visually demonstrate the shape of the electron shells predicted by quantum mechanics.
With other instruments, scanning tunneling microscopes, individual atoms can not only be seen, but also moved to the desired location. About a month ago, this technique allowed IBM engineers to draw a cartoon, each frame of which is composed of atoms: such artistic experiments do not have any practical effect, but demonstrate the fundamental possibility of manipulating atoms. For applied purposes, it is no longer an atomic assembly that is used, but chemical processes with self-organization of nanostructures or self-limitation of the growth of monatomic layers on a substrate.
Hydrogen atom capturing electron clouds. And although modern physicists with the help of accelerators can even determine the shape of a proton, the hydrogen atom, apparently, will remain the smallest object, the image of which it makes sense to call a photograph. "Lenta.ru" presents an overview of modern methods of photographing the microworld.
Strictly speaking, ordinary photography is almost gone these days. The images that we habitually call photographs and can find, for example, in any photo reportage of "Lenta.ru", in fact, are computer models. A light-sensitive matrix in a special device (traditionally it is still called a "camera") determines the spatial distribution of light intensity in several different spectral ranges, the control electronics stores this data in digital form, and then another electronic circuit based on these data gives a command to the transistors in the liquid crystal display ... Film, paper, special solutions for their processing - all this has become exotic. And if we remember the literal meaning of the word, then photography is "light painting". So what to say about what scientists have succeeded to photograph atom, it is possible only with a fair amount of convention.
More than half of all astronomical images have long been taken by infrared, ultraviolet and X-ray telescopes. Electron microscopes are irradiated not with light, but with an electron beam, and atomic-force microscopes do scan the relief of the sample with a needle. There are X-ray microscopes and magnetic resonance imaging machines. All these devices give us accurate images of various objects, and despite the fact that there is no need to talk about "light painting" here, of course, we still dare to call such images photographs.
Physicists' experiments to determine the shape of a proton or the distribution of quarks within particles will remain behind the scenes; our story will be limited to the scale of atoms.
Optics never age
As it turned out in the second half of the 20th century, optical microscopes still have a lot to develop. A defining moment in biological and medical research has been the emergence of fluorescent dyes and methods for selectively labeling certain substances. It wasn’t just new paint, it was a real revolution.
Contrary to popular belief, fluorescence is not a glow in the dark at all (the latter is called luminescence). This is the phenomenon of absorption of quanta of a certain energy (say, blue light), followed by the emission of other quanta of lower energy and, accordingly, a different light (when blue is absorbed, green ones will be emitted). If you put in a filter that allows only the quanta emitted by the dye to pass through and traps the light that causes fluorescence, you can see a dark background with bright spots of dyes, and the dyes, in turn, can color the sample extremely selectively.
For example, you can paint the cytoskeleton of a nerve cell red, highlight synapses green, and the nucleus blue. You can make a fluorescent label, which will allow you to detect protein receptors on the membrane or molecules synthesized by the cell under certain conditions. Immunohistochemical staining has revolutionized biological science. And when genetic engineers learned to make transgenic animals with fluorescent proteins, this method experienced a rebirth: for example, mice with neurons painted in different colors became a reality.
In addition, engineers have come up with (and worked out in practice) a method of the so-called confocal microscopy. Its essence lies in the fact that the microscope focuses on a very thin layer, and a special diaphragm cuts off the illumination created by objects outside this layer. Such a microscope can sequentially scan a sample from top to bottom and obtain a stack of images, which is a ready-made basis for a three-dimensional model.
The use of lasers and sophisticated optical beam control systems has solved the problem of dye burnout and drying of delicate biological samples under bright light: the laser beam scans the sample only when it is necessary for shooting. And in order not to waste time and effort on examining a large specimen through an eyepiece with a narrow field of view, the engineers proposed an automatic scanning system: you can put a glass with a specimen on the stage of a modern microscope, and the device will independently shoot a large-scale panorama of the entire specimen. At the same time, in the right places, he will focus, and then glue a lot of frames together.
Some microscopes can fit live mice, rats, or at least small invertebrates. Others give a slight increase, but are combined with an X-ray machine. Many of them are mounted on special tables weighing several tons in rooms with carefully controlled microclimate to eliminate vibration disturbances. The cost of such systems exceeds the cost of other electron microscopes, and contests for the most beautiful frame have long become a tradition. In addition, the improvement of optics continues: from the search for the best types of glass and the selection of optimal combinations of lenses, engineers have moved to methods of focusing light.
We have specifically listed a number of technical details in order to show that progress in biological research has long been associated with progress in other areas. If there were no computers capable of automatically counting the number of stained cells in several hundred photographs, there would be little use for supermicroscopes. And without fluorescent dyes, all millions of cells would be indistinguishable from each other, so it would be almost impossible to trace the formation of new ones or the death of old ones.
In fact, the first microscope was a clamp with a spherical lens attached to it. An analogue of such a microscope can be a simple playing card with a hole made in it and a drop of water. According to some reports, similar devices were used by gold miners in Kolyma already in the last century.
Beyond the diffraction limit
Optical microscopes have a fundamental drawback. The fact is that it is impossible to restore the shape of those objects, which turned out to be much smaller than the wavelength, from the shape of the light waves: you can just as well try to investigate the fine texture of the material with your hand in a thick glove for welding.
The limitations created by diffraction were partially overcome, and without violating the laws of physics. Two circumstances help optical microscopes to dive under the diffraction barrier: the fact that, during fluorescence, quanta are emitted by individual dye molecules (which can be quite far apart from each other), and the fact that, due to the superposition of light waves, it is possible to obtain a bright spot with a diameter smaller than wavelength.
When superimposed on each other, the light waves are able to mutually extinguish each other, therefore, the illumination parameters of the sample so that the smallest possible area falls into the bright area. In combination with mathematical algorithms that allow, for example, to remove ghosting, such directional lighting gives a sharp increase in the quality of shooting. It becomes possible, for example, to examine intracellular structures with an optical microscope and even (by combining the described method with confocal microscopy) to obtain their three-dimensional images.
Electron microscope to electronic devices
In order to discover atoms and molecules, scientists did not have to look at them - molecular theory did not need to see an object. But microbiology became possible only after the invention of the microscope. Therefore, at first, microscopes were associated precisely with medicine and biology: physicists and chemists, who studied much smaller objects, managed by other means. When they also wanted to look at the microcosm, diffraction limitations became a serious problem, especially since the methods of fluorescence microscopy described above were still unknown. And there is little sense in increasing the resolution from 500 to 100 nanometers, if the object to be examined is even smaller!
Knowing that electrons can behave both as a wave and as a particle, physicists from Germany in 1926 created an electronic lens. The idea underlying it was very simple and understandable to any schoolchild: since the electromagnetic field deflects electrons, it can be used to change the shape of the beam of these particles by pulling them apart, or, on the contrary, to reduce the beam diameter. Five years later, in 1931, Ernst Ruska and Max Knoll built the world's first electron microscope. In the device, the sample was first illuminated by a beam of electrons, and then an electron lens expanded the transmitted beam before it fell on a special luminescent screen. The first microscope gave a magnification of only 400 times, but replacing light with electrons opened the way to photography with a magnification of hundreds of thousands of times: the designers had only to overcome several technical obstacles.
The electron microscope made it possible to examine the structure of cells in a previously unattainable quality. But from this picture it is impossible to understand the age of cells and the presence of certain proteins in them, and this information is very necessary for scientists.
Electron microscopes now allow close-up photography of viruses. There are various modifications of devices that allow not only to see through thin sections, but also to view them in "reflected light" (in reflected electrons, of course). We will not go into detail about all versions of microscopes, but note that recently researchers have learned how to reconstruct an image from a diffraction pattern.
Touch, not consider
Another revolution has come from a further departure from the "light and see" principle. The atomic force microscope, as well as the scanning tunneling microscope, no longer shines on the surface of the samples. Instead, an especially thin needle moves across the surface, which literally bounces even on irregularities the size of an individual atom.
Without going into the details of all such methods, we note the main thing: the tip of a tunneling microscope can not only be moved along the surface, but also used to rearrange atoms from place to place. This is how scientists create inscriptions, drawings and even cartoons in which a painted boy plays with an atom. A real xenon atom, dragged by the tip of a scanning tunneling microscope.
Tunneling microscope is called because it uses the effect of tunneling current flowing through the tip: electrons pass through the gap between the tip and the surface due to the tunneling effect predicted by quantum mechanics. Such a device requires a vacuum to operate.
The atomic force microscope (AFM) is much less demanding on the surrounding conditions - it can (with a number of limitations) operate without air evacuation. In a sense, the AFM is the nanotechnological successor to the gramophone. A needle mounted on a thin and flexible cantilever arm ( cantilever and there is a "bracket"), moves along the surface without applying voltage to it and follows the relief of the sample in the same way as the gramophone needle follows along the grooves of a gramophone record. The bending of the cantilever forces the mirror fixed on it to deflect, the mirror deflects the laser beam, and this allows very accurate determination of the shape of the sample under study. The main thing is only to have a sufficiently accurate system for moving the needle, as well as a supply of needles that must be perfectly sharp. The radius of curvature at the tips of such needles may not exceed one nanometer.
AFM allows you to see individual atoms and molecules, however, like a tunnel microscope, it does not allow you to look under the surface of the sample. In other words, scientists have to choose between the ability to see atoms and the ability to study the entire object as a whole. However, even for optical microscopes, the insides of the samples under study are not always accessible, because minerals or metals usually transmit light poorly. In addition, difficulties still arise with photographing atoms - these objects appear as simple balls, the shape of electron clouds is not visible in such photographs.
Synchrotron radiation generated by the deceleration of charged particles accelerated by accelerators makes it possible to study the fossilized remains of prehistoric animals. By rotating a sample under X-rays, we can get three-dimensional tomograms - this is how, for example, the brain inside the skull of fish, which became extinct 300 million years ago, was found. Rotation can also be dispensed with if the transmitted radiation is recorded by the fixation of X-rays scattered due to diffraction.
And this is not all the possibilities that X-ray radiation opens up. When irradiated with it, many materials fluoresce, and by the nature of the fluorescence it is possible to determine the chemical composition of the substance: in this way scientists color the ancient artifacts, the works of Archimedes erased in the Middle Ages, or the color of feathers of long-extinct birds.
Atoms posing
Against the background of all the possibilities offered by X-ray or optical-fluorescent methods, a new way of photographing individual atoms does not seem to be such a big breakthrough in science. The essence of the method, which made it possible to obtain the images presented this week, is as follows: electrons are stripped from ionized atoms and sent to a special detector. Each act of ionization strips an electron from a certain position and gives one point in the "photograph". Having accumulated several thousand such points, scientists have formed a picture showing the most probable places of detecting an electron around the nucleus of an atom, and this, by definition, is an electron cloud.
In conclusion, let us say that the ability to see individual atoms with their electron clouds is rather the icing on the cake of modern microscopy. It was important for scientists to investigate the structure of materials, to study cells and crystals, and the resulting development of technology made it possible to reach the hydrogen atom. Anything less is already the sphere of interest of specialists in particle physics. And biologists, materials scientists and geologists still have room to improve microscopes, even with a rather modest magnification against the background of atoms. Specialists in neurophysiology, for example, have long wanted to have a device that can see individual cells inside a living brain, and the creators of rovers would sell their souls for an electron microscope that would climb aboard a spacecraft and could work on Mars.
As you know, everything material in the Universe consists of atoms. An atom is the smallest unit of matter that carries its properties. In turn, the structure of the atom is made up of the magic trinity of microparticles: protons, neutrons and electrons.
Moreover, each of the microparticles is universal. That is, you cannot find two different protons, neutrons or electrons in the world. They are all absolutely alike. And the properties of the atom will depend only on the quantitative composition of these microparticles in the general structure of the atom.
For example, the structure of a hydrogen atom consists of one proton and one electron. Next in complexity, the helium atom is made up of two protons, two neutrons, and two electrons. The lithium atom is made up of three protons, four neutrons and three electrons, etc.
Atomic structure (from left to right): hydrogen, helium, lithium
Atoms combine into molecules, and molecules - into substances, minerals and organisms. The DNA molecule, which is the basis of all living things, is a structure assembled from the same three magic bricks of the universe as a stone lying on the road. Although this structure is much more complex.
Even more surprising facts are revealed when we try to take a closer look at the proportions and structure of the atomic system. It is known that an atom consists of a nucleus and electrons moving around it along a trajectory that describes a sphere. That is, it cannot even be called a movement in the usual sense of the word. The electron is rather found everywhere and immediately within this sphere, creating an electron cloud around the nucleus and forming an electromagnetic field.
Schematic representations of the structure of the atom
The nucleus of an atom consists of protons and neutrons, and almost all the mass of the system is concentrated in it. But at the same time, the nucleus itself is so small that if you increase its radius to a scale of 1 cm, then the radius of the entire atomic structure will reach hundreds of meters. Thus, everything that we perceive as dense matter consists of more than 99% of energy connections between physical particles and less than 1% of the physical forms themselves.
But what are these physical forms? What are they made of, and how material are they? To answer these questions, let's take a closer look at the structures of protons, neutrons and electrons. So, we descend one more step into the depths of the microworld - to the level of subatomic particles.
What does an electron consist of?
The smallest particle in an atom is an electron. An electron has mass, but it has no volume. In the scientific view, the electron does not consist of anything, but is a structureless point.
An electron cannot be seen under a microscope. It is observed only in the form of an electron cloud, which looks like a blurry sphere around the atomic nucleus. At the same time, it is impossible to say with accuracy where the electron is at the moment of time. Devices are able to capture not the particle itself, but only its energy trace. The essence of the electron is not embedded in the concept of matter. Rather, it is like a kind of empty form that exists only in motion and due to motion.
So far, no structure has been found in the electron. It is the same pointlike particle as a quantum of energy. In fact, the electron is energy, however, it is a more stable form of it than that which is represented by the photons of light.
At the moment, the electron is considered indivisible. This is understandable, because it is impossible to divide what has no volume. However, in theory there are already developments, according to which the composition of the electron contains the triunity of such quasiparticles as:
- Orbiton - contains information about the orbital position of the electron;
- Spinon is responsible for spin or torque;
- Holon - carries information about the charge of an electron.
However, as we can see, quasiparticles with matter no longer have absolutely nothing in common, and carry only one information.
Photos of atoms of different substances in an electron microscope
Interestingly, an electron can absorb quanta of energy, such as light or heat. In this case, the atom moves to a new energy level, and the boundaries of the electron cloud expand. It also happens that the energy absorbed by the electron is so great that it can jump out of the atomic system, and then continue its motion as an independent particle. At the same time, it behaves like a photon of light, that is, it seems to cease to be a particle and begins to manifest the properties of a wave. This has been proven experimentally.
Jung's experiment
In the course of the experiment, a stream of electrons was directed onto a screen with two slits cut through it. Passing through these slots, electrons collided with the surface of another - projection - screen, leaving their mark on it. As a result of such "bombardment" with electrons, an interference pattern appeared on the projection screen, similar to that which would appear if waves, but not particles, would pass through the two slits.
Such a pattern arises due to the fact that a wave, passing between two slots, is divided into two waves. As a result of further movement, the waves overlap each other, and in some areas their mutual damping occurs. As a result, we get many stripes on the projection screen, instead of one as it would be if the electron behaved like a particle.
The structure of the nucleus of an atom: protons and neutrons
Protons and neutrons make up the nucleus of an atom. And despite the fact that the core occupies less than 1% of the total volume, it is in this structure that almost the entire mass of the system is concentrated. But at the expense of the structure of protons and neutrons, physicists were divided, and at the moment there are two theories at once.
- Theory # 1 - Standard
The Standard Model says that protons and neutrons are made up of three quarks connected by a cloud of gluons. Quarks are point particles, just like quanta and electrons. And gluons are virtual particles that ensure the interaction of quarks. However, neither quarks nor gluons have been found in nature, therefore this model lends itself to severe criticism.
- Theory # 2 - Alternative
But according to the alternative theory of a unified field, developed by Einstein, a proton, like a neutron, like any other particle of the physical world, is an electromagnetic field rotating at the speed of light.
Human and planet electromagnetic fields
What are the principles of the structure of the atom?
Everything in the world - thin and dense, liquid, solid and gaseous - is only the energy states of countless fields that permeate the space of the Universe. The higher the level of energy in the field, the thinner and less perceptible it is. The lower the energy level, the more stable and tangible it is. In the structure of the atom, as in the structure of any other unit of the Universe, there is the interaction of such fields - different in energy density. It turns out that matter is only an illusion of the mind.
However, photographing the atom itself, and not any part of it, seemed to be an extremely difficult task, even with the use of the most high-tech devices.
The fact is that according to the laws of quantum mechanics, it is impossible to equally accurately determine all the properties of a subatomic particle. This section of theoretical physics is built on the Heisenberg uncertainty principle, which states that it is impossible to equally accurately measure the coordinates and momentum of a particle - accurate measurements of one property will certainly change the data about another.
Therefore, instead of locating (the coordinates of the particle), quantum theory proposes to measure the so-called wave function.
The wave function works in much the same way as the sound wave. The only difference is that the mathematical description of a sound wave determines the movement of molecules in the air at a certain place, and the wave function describes the probability of a particle appearing in a particular place according to the Schrödinger equation.
Measuring the wave function is also difficult (direct observations lead to its collapse), but theoretical physicists can roughly predict its values.
It is possible to experimentally measure all the parameters of the wave function only if it is collected from separate destructive measurements carried out on completely identical systems of atoms or molecules.
Physicists from the Dutch research institute AMOLF have presented a new method that does not require any "restructuring", and published the results of their work in the journal Physical Review Letters. Their methodology is based on the 1981 hypothesis of three Soviet theoretical physicists, as well as on later studies.
During the experiment, a team of scientists directed two laser beams at hydrogen atoms, placed in a special chamber. As a result of this effect, the electrons left their orbits with the speed and direction that were determined by their wave functions. A strong electric field in the chamber, where the hydrogen atoms were located, directed electrons to certain parts of the planar (flat) detector.
The position of the electrons hitting the detector was determined by their initial velocity, not by their position in the chamber. Thus, the distribution of electrons on the detector told scientists about the wave function of these particles, which they had when they left the orbit of the nucleus of the hydrogen atom.
The movements of electrons were displayed on a phosphorescent screen in the form of dark and light rings, which the scientists photographed with a high-resolution digital camera.
"We are very pleased with our results. Quantum mechanics has so little to do with people's daily lives that hardly anyone would have thought of taking a real photograph of quantum interactions in the atom," says lead author Aneta Stodolna. She also claims that the developed technique can have practical applications, for example, for creating conductors as thick as an atom, the development of molecular wire technology, which significantly improves modern electronic devices.
“It is noteworthy that the experiment was carried out precisely on hydrogen - at the same time the simplest and most widespread substance in our Universe. It will be necessary to understand whether this technique can be applied to more complex atoms. but also nanotechnology, "says Jeff Lundeen of the University of Ottawa, who was not involved in the study.
However, the scientists themselves who conducted the experiment do not think about the practical side of the issue. They believe that their discovery is primarily related to fundamental science, which will help transfer more knowledge to future generations of physicists.
PostNauka debunks scientific myths and explains common misconceptions. We asked our experts to comment on popular ideas about the structure and properties of atoms.
Rutherford's model corresponds to modern ideas about the structure of the atom
This is true, but in part. The planetary model of the atom, in which light electrons revolve around a heavy core, like planets around the Sun, was proposed by Ernest Rutherford in 1911, after the nucleus itself was discovered in his laboratory. By bombarding a sheet of metal foil with alpha particles, the scientists found that the vast majority of particles pass through the foil, like light through glass. However, a small fraction of them - about one in 8000 - were reflected back to the source. Rutherford explained these results by the fact that the mass is not evenly distributed in matter, but is concentrated in "clumps" - atomic nuclei that carry a positive charge that repels positively charged alpha particles. Light negatively charged electrons avoid "falling" on the nucleus by rotating around them, so that the centrifugal force balances the electrostatic attraction.
It is said that, upon inventing this model, Rutherford exclaimed: "Now I know what an atom looks like!" However, soon, following inspiration, Rutherford realized the flawedness of his idea. Rotating around the nucleus, the electron creates around itself alternating electric and magnetic fields. These fields propagate at the speed of light in the form of an electromagnetic wave. And such a wave carries with it energy! It turns out that, revolving around the nucleus, the electron will continuously lose energy and within billionths of a second will fall on the nucleus. (The question may arise, is it possible to apply the same argument to the planets of the solar system: why do they not fall on the sun? Answer: gravitational waves, if they exist at all, are much weaker than electromagnetic ones, and the energy stored in the planets is much greater than in electrons, so the "power reserve" of the planets is many orders of magnitude longer.)
Rutherford instructed his collaborator, the young theoretician Niels Bohr, to resolve the contradiction. After working for two years, Bohr found a partial solution. He postulated that among all possible orbits of the electron there are those on which the electron can be for a long time without emitting. An electron can move from one stationary orbit to another, while absorbing or emitting a quantum of the electromagnetic field with an energy equal to the difference between the energies of the two orbits. Using the initial principles of quantum physics, which had already been discovered by that time, Bohr was able to calculate the parameters of stationary orbits and, accordingly, the energies of radiation quanta corresponding to transitions. By that time, these energies were measured using spectroscopic methods, and Bohr's theoretical predictions coincided almost perfectly with the results of these measurements!
Despite this triumphant result, Bohr's theory hardly clarified the issue of atomic physics, because it was semi-empirical: postulating the existence of stationary orbits, it did not explain their physical nature in any way. An in-depth explanation of the issue required at least two decades more, during which quantum mechanics was developed as a systematic, integral physical theory.
Within the framework of this theory, the electron obeys the principle of uncertainty and is described not by a material point, like a planet, but by a wave function "smeared" over the entire orbit. At each moment of time, it is in a superposition of states corresponding to all points of the orbit. Since the density of mass distribution in space, determined by the wave function, does not depend on time, an alternating electromagnetic field around the electron is not created; there is no energy loss.
Thus, the planetary model gives a correct visual representation of what an atom looks like - Rutherford was right in his exclamation. However, it does not provide an explanation of how the atom works: this device is much more complex and deeper than something that Rutherford modeled.
In conclusion, I would like to note that the "myth" of the planetary model is at the very center of the intellectual drama that gave rise to a turning point in physics a hundred years ago and to a large extent shaped this science in its modern form.
Alexander Lvovsky
PhD in Physics, professor at the Faculty of Physics at the University of Calgary, head of the scientific group, member of the scientific council of the Russian Quantum Center, editor of the scientific journal Optics Express
Individual atoms can be controlled
This is true. Of course you can, why not? You can control different parameters of the atom, and the atom has a lot of them: it has a position in space, velocity, and there are also internal degrees of freedom. The internal degrees of freedom determine the magnetic and electrical properties of the atom, as well as the willingness to emit light or radio waves. Depending on the internal state of an atom, it can be more or less active in collisions and chemical reactions, change the properties of surrounding atoms, and its response to external fields depends on its internal state. In medicine, for example, the so-called polarized gases are used to construct tomograms of the lungs - in such gases all atoms are in the same internal state, which makes it possible to "see" the volume filled by them by their response.
Controlling the speed of an atom or its position is not so difficult; it is much more difficult to select exactly one atom for control. But this can also be done. One of the approaches to such an atom separation is realized with the help of laser cooling. For control, it is always convenient to have a known initial position; it is very good if the atom is still not moving at the same time. Laser cooling allows you to achieve both, localize atoms in space and cool them, that is, reduce their speed to almost zero. The principle of laser cooling is the same as that of a jet plane, only the latter emits a jet of gas to accelerate, and in the first case, the atom, on the contrary, absorbs a stream of photons (light particles) and decelerates. Modern methods of laser cooling allow millions of atoms to be cooled down to pedestrian speeds and below. Next, various kinds of passive traps come into play, for example, a dipole trap. If a light field is used for laser cooling, which the atom actively absorbs, then to keep it in a dipole trap, the frequency of the light is selected far from any absorption. It turns out that highly focused laser light is capable of polarizing small particles and dust particles and pulling them into the region of the highest light intensity. The atom is no exception and is also drawn into the region of the strongest field. It turns out that if you focus the light as strongly as possible, then only exactly one atom can be kept in such a trap. The fact is that if the second falls into the trap, then he is so strongly pressed against the first that they form a molecule and at the same time fall out of the trap. However, such sharp focusing is not the only way to isolate a single atom; you can also use the properties of the interaction of an atom with a resonator for charged atoms, ions, you can use electric fields to capture and confine exactly one ion, and so on. One can even excite one atom in a rather limited ensemble of atoms into a very highly excited, so-called Rydberg state. An atom, once excited to the Rydberg state, blocks the possibility of exciting its neighbors to the same state and, if the volume with atoms is small enough, it will be unique.
One way or another, after the atom is trapped, it can be manipulated. The internal state can be changed by light and radio frequency fields, using the desired frequencies and polarization of the electromagnetic wave. It is possible to transfer an atom to any predetermined state, be it a certain state - a level or their superposition. The only question is the availability of the necessary frequencies and the ability to make sufficiently short and powerful control pulses. Recently, it became possible to more efficiently control atoms, keeping them in the vicinity of nanostructures, which allows not only to "talk" with the atom more efficiently, but also to use the atom itself - more precisely, its internal states - to control the flows of light, and in the future, perhaps , and for computational purposes.
Controlling the position of an atom held by a trap is a very simple task - just move the trap itself. In the case of a dipole trap, move the light beam, which can be done, for example, with movable mirrors for a laser show. The speed of the atom can be given again in a reactive way - to make it absorb light, and the ion can easily be dispersed by electric fields, just as it was done in cathode-ray tubes. So today, in principle, anything can be done with the atom, it’s just a matter of time and effort.
Alexey Akimov
Atom is indivisible
Partly true, partly not. Wikipedia gives us the following definition: “Atom (from ancient Greek ἄτομος - indivisible, uncut) is a particle of matter of microscopic size and mass, the smallest part of a chemical element, which is the carrier of its properties. An atom consists of an atomic nucleus and electrons. "
Any educated person now represents an atom in Rutherford's model, summarized in the last sentence of this generally accepted definition. It would seem that the answer to this question / myth is obvious: an atom is a composite and complex object. However, the situation is not so straightforward. The ancient philosophers put into the definition of the atom rather the meaning of the existence of an elementary and indivisible particle of matter and hardly connected the problem with the structure of the elements of the periodic table. In Rutherford's atom we really find such a particle - it's an electron.
Electron in accordance with modern concepts that fit into the so-called
«> The Standard Model is a point, the state of which is described by position and speed. It is important that the simultaneous assignment of these kinematic characteristics is impossible due to the Heisenberg uncertainty principle, but considering only one of them, for example, a coordinate, it is possible to determine it with an arbitrarily high accuracy.
Is it possible then, using modern experimental techniques, to try to localize an electron on a scale significantly smaller than the atomic size (~ 0.5 * 10-8 cm), and check its point-like nature? It turns out that when trying to localize an electron on the scale of the so-called Compton wavelength - about 137 times smaller than the size of a hydrogen atom - the electron will interact with its antimatter and the system will become unstable.
The point and indivisibility of the electron and other elementary particles of matter is a key element of the principle of short-range interaction in field theory and is present in all fundamental equations describing nature. Thus, the ancient philosophers were not so far from the truth, assuming that indivisible particles of matter exist.
Dmitry Kupriyanov
Doctor of Physical and Mathematical Sciences, Professor of Physics, St. Petersburg State Polytechnic University, Head. Department of Theoretical Physics, SPbSPU
This is still unknown to science. The planetary model of the atom, proposed by Rutherford, assumed that electrons revolve around an atomic nucleus, like planets revolving around the sun. In this case, it was natural to assume that electrons are solid spherical particles. Rutherford's classic model was self-contradictory. Obviously, moving accelerated charged particles (electrons) would have to lose energy due to electromagnetic radiation and ultimately fall on the nuclei of atoms.
Niels Bohr proposed to prohibit this process and introduce certain requirements for the radii of the orbits along which the electrons move. Bohr's phenomenological model gave way to the quantum model of the atom, developed by Heisenberg, and the quantum, but more visual model of the atom, proposed by Schrödinger. In Schrödinger's model, electrons are no longer balls flying in an orbit, but standing waves that, like clouds, hang over the atomic nucleus. The shape of these "clouds" was described by the wave function introduced by Schrödinger.
The question immediately arose: what is the physical meaning of the wave function? The answer was suggested by Max Born: the square of the modulus of the wave function is the probability of finding an electron at a given point in space. And here the difficulties began. The question arose: what does it mean to find an electron at a given point in space? Shouldn't Born's statement be understood as a recognition that an electron is a small ball that flies along a certain trajectory and which can be caught at a certain point on this trajectory with a certain probability?
This is the point of view that Schrodinger and Albert Einstein, who joined him in this matter, adhered to. They were opposed by the physicists of the Copenhagen School - Niels Bohr and Werner Heisenberg, who argued that the electron simply does not exist between the events of measurement, which means that it makes no sense to talk about the trajectory of its motion. Bohr and Einstein's discussion of the interpretation of quantum mechanics has gone down in history. The winner seemed to be Bohr: he managed, although not very clearly, to refute all the paradoxes formulated by Einstein, and even the famous paradox of "Schrödinger's cat" formulated by Schrödinger in 1935. For several decades, most physicists agreed with Bohr that matter is not an objective reality given to us in sensations, as Karl Marx taught, but something that arises only at the moment of observation and does not exist without an observer. Interestingly, in Soviet times, philosophy departments at universities taught that such a point of view is subjective idealism, that is, a trend that runs counter to objective materialism - the philosophy of Marx, Engels, Lenin and Einstein. At the same time, at the physics departments, students were taught that the concepts of the Copenhagen School are the only correct ones (perhaps because the most famous Soviet theoretical physicist, Lev Landau, belonged to this school).
At the moment, the opinions of physicists are divided. On the one hand, the Copenhagen interpretation of quantum mechanics continues to be popular. Attempts to experimentally test the validity of this interpretation (for example, the successful test of the so-called Bell inequality by the French physicist Alain Aspe) enjoy almost unanimous approval from the scientific community. On the other hand, theorists quite calmly discuss alternative theories, such as the theory of parallel worlds. Returning to the electron, we can say that its chances of remaining a billiard ball are not very high yet. At the same time, they are nonzero. In the 1920s, it was the billiard model of Compton scattering that made it possible to prove that light consists of quanta - photons. In many problems related to important and useful devices (diodes, transistors), it is convenient to consider the electron as a billiard ball. The wave nature of the electron is important for describing more subtle effects, for example, the negative magnetoresistance of metals.
The philosophical question of whether a ball-electron exists between the acts of measurement is not of great importance in ordinary life. However, this question continues to be one of the most serious problems of modern physics.
Alexey Kavokin
PhD in Physics and Mathematics, Professor at the University of Southampton, Head of the Quantum Polaritonics Group of the Russian Quantum Center, Scientific Director of the Mediterranean Institute of Fundamental Physics (Italy)
An atom can be completely destroyed
This is true. Break not build. Anything can be destroyed, including an atom, with any degree of completeness. An atom in the first approximation is a positively charged nucleus surrounded by negatively charged electrons. The first destructive action that can be performed with respect to an atom is to tear off electrons from it. This can be done in different ways: you can focus powerful laser radiation on it, you can irradiate it with fast electrons or other fast particles. An atom that has lost some of its electrons is called an ion. It is in this state that atoms reside on the Sun, where the temperatures are so high that it is practically impossible for atoms to preserve their electrons in collisions.
The more electrons an atom has lost, the more difficult it is to rip off the rest. Depending on the atomic number, an atom has more or less electrons. The hydrogen atom has only one electron, and it often loses it even under normal conditions, and it is the hydrogen that has lost its electrons that determines the pH of water. The helium atom has two electrons, and in a fully ionized state is called alpha particles - we already expect such particles from a nuclear reactor rather than from ordinary water. Atoms containing many electrons require even more energy to remove all electrons, but nevertheless, you can remove all electrons from any atom.
If all the electrons are torn off, then the nucleus remains, but it can also be destroyed. The nucleus consists of protons and neutrons (generally hadrons), and although they are quite strongly coupled, an incident particle of sufficiently high energy can tear them apart. Heavy atoms, in which there are too many neutrons and protons, tend to fall apart on their own, releasing quite a lot of energy - this is the principle nuclear power plants are based on.
But even if the nucleus is broken, all the electrons are torn off, the original particles remain: neutrons, protons, electrons. They can, of course, be destroyed too. Actually, this is what he does, which accelerates protons to huge energies, completely destroying them in collisions. At the same time, a lot of new particles are born, which the collider studies. The same can be done with electrons and with any other particles.
The energy of the destroyed particle does not disappear, it is distributed among other particles, and if there are enough of them, then it becomes impossible to quickly trace the original particle in the sea of new transformations. Everything can be destroyed, there are no exceptions.
Alexey Akimov
PhD in Physics and Mathematics, Head of the Quantum Simulators group of the Russian Quantum Center, lecturer at the Moscow Institute of Physics and Technology, employee of the Lebedev Physical Institute, researcher at Harvard University