Atom, the earliest abstract ontological significance of philosophy. As a microscopic particle exists, atomic neither see nor touched, which gives them a glimmer of mystery and sense of distance. With the advancement of human knowledge, atom abstraction from becoming a scientific theory. An atom consists of a nucleus and some surrounding dense surrounding the nucleus of negatively charged electrons. Electron motion around the nucleus, releasing energy, so that the whole atoms formed integrally with the outside world, continue energy exchange with the outside world is formed, the entire atom is in motion, the movement of atoms is the blood of the atom. Around us, so a group of atoms, they are cold surface, but its heart is absolutely gentle, they are called cold atoms. Before saying cold atoms, we start to understand the corresponding heat under the cold cold What is an atom? What is the nature of heat? Learn more about what kind of cold atoms can be called atoms? Cold atoms is how to achieve?
Hot nature
Hot concept we are all familiar, such as this past summer, the high temperature for a month Shaanxi, really fast heating, but the heat in this sense is "hot" in a way that we talk about everyday, so everyday and heat can not express the essence of the nature of heat, in other words, here we need to understand the science of physics "hot." In 1745, Russian scientist Lomonosov revealed the nature of heat: Heat is the phenomenon of movement, that is hot is the object of microscopic particles velocity speed performance! Classical thermodynamics tells us, between the temperature of the object and the speed of moving atom a simple relationship that the temperature is proportional to the square of the speed. We are talking here of cold atoms, the concept of thermodynamics.
Under normal circumstances, cold and heat is always relative, what kind of cold atoms can be called atoms it? Roughest requirement is -273 ℃, if expressed in absolute temperature, the general requirement is that the order of a few milli-Kelvin, another high-end point is the micro-Kelvin even colder. Cold atoms moving speed is slow, more stable, more accurate atomic level structure and narrower transition spectra, as compared with a clearer hot atom quantum state. Currently, the use of cold atoms produced the most accurate atomic clocks internationally - strontium atoms in optical lattice clock 160 million years before the error 1 second.
How cold atoms?
Our usual way of life is a refrigerator to cool objects, it is not possible to get into the freezer cold atomic atoms of it? Of course, not so simple. We know that the best cooling effect can be achieved household refrigerator is -20 ℃, it seems refrigerator to cool atoms to be not work. So what special measures need to be prepared by means of cold atoms it? Physicist Steven Chu, Cohen - Da Nuoji, Phillips revealed the answer for us. They pioneered the use of the laser gas is cooled to a temperature range ajar method that atom high power laser pointer cooling and trapping atoms cooled to prisoners or arrested in different types of "atom trap", they also won the 1997 Nobel Prize in Physics.
Laser cooling of atoms is how to achieve? We give a simple example to illustrate vividly. We know that light is both the fluctuation characteristics, but also has particle properties that wave-particle duality of light. Therefore, in the process of laser-cooled atoms, we are a bunch of laser as a stream of particles, such particles called photons. Now began to formulate a scenario where you stand on the open road, there is the face of a free-running car (ignoring friction), in order to reduce the speed of the car, you can continue to throw stones to the car, the car received a small stone, will random stone thrown out in all directions, in considering the overall effect of the car received many threw small stones, the speed is gradually slowed down. Laser cooling atoms with photons can be considered to "hit" atomic offset speed atoms. Of course, laser cooling is essentially a more complex physical processes, scientists called Doppler cooling.
It appears atom laser cooling technology to achieve a long time human manipulation and control of atoms on a microscopic scale dream, so the microscopic world of atoms away from us closer. Then follow our lens to observe and feelings hidden in the microscopic world of cold atoms gentle it!
The figure presented is a strontium atomic vapor under high temperature of 500 degrees Celsius, and cooling by laser deceleration in the magneto-optical trap was captured live scene. The whole process is in a high vacuum chamber of completion. With the photo window reflection laser cavity to form a concentric a ring, The cold atomic group focused on the center of the circle, bright spot in the center is the most cold FIG radicals.
This picture show is under the laser and magnetic field interaction prisoners trapped and cooled strontium atoms. In this case we use a laser to control the radicals, radicals showing a heart-shaped. In fact, the radicals can be formed not only heart-shaped, when strontium atoms after laser cooling, is captured in a magneto-optical trap, then cooled Gatling laser with respect to the change in the resonance frequency of the atomic frequency offset (mismatch), the radicals will be showing different shapes in the figure, the more cooling laser atomic resonance frequency detuning is large, the role of gravity in the atoms sink to the bottom, showing the crescent-shaped, like most of the new moon.
Grand cosmic evolution demonstrating the vast beauty of science, with its subtle atomic exquisite show the beauty of the microscopic world of science. Hard sciences also hidden in the soft part of those who bring in the soft part of the visual surprises us, but also allows us to appreciate rigorous scientific research bears and have fun!
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