РОССИЙСКАЯ АКАДЕМИЯ НАУК

УРАЛЬСКОЕ ОТДЕЛЕНИЕ

ИНСТИТУТ ХИМИИ TBEPДОГО ТЕЛА
   
| | | | |
| | | |
 07.06.2007   Карта сайта     Language По-русски По-английски
Новые материалы
Экология
Электротехника и обработка материалов
Медицина
Статистика публикаци


07.06.2007

Researchers Catch Motion of a Single Electron on Video



Using pulses of high-intensity sound, two Brown University physicists have succeeded in making a movie showing the motion of a single electron. Humphrey Maris, a physics professor at Brown University, and Wei Guo, a Brown doctoral student, were able to film the electron as it moved through a container of superfluid helium.


PROVIDENCE, R.I. [Brown University] — To observe the motion of an electron – an elementary particle with a mass that is one billionth of a billionth of a billionth of a gram – has been considered to be impossible. So when two Brown University physicists showed movies of electrons moving through liquid helium at the 2006 International Symposium on Quantum Fluids and Solids in Kyoto, they raised some eyebrows.


The images, which were published online on April 28, 2007, in the Journal of Low Temperature Physics, show scattered points of light moving down the screen – some in straight lines, some following a snakelike path. The Matrix it’s not. Still, the fact that they can be seen at all is astounding. “We were astonished when we first saw an electron moving across the screen,” said Humphrey Maris, a professor of physics at Brown University. “Once we had the idea, setting it up was surprisingly easy.”


Image




Electrons: The Video
Captured on a home video camera, some electrons follow a straight path through superfluid helium (far left). Those entrained in a superfluid vortex follow a snakelike path.
Image: Humphrey Maris and Wei Guo





Maris and Wei Guo, a doctoral student, took advantage of the bubbles that form around electrons in supercold liquid helium. Using sound waves to expand the bubbles and a coordinated strobe light to illuminate them, Guo was able to catch their movements on a home video camera.


A free electron repels the atoms that surround it, creating a small space, or bubble, around itself. In conventional liquids, the bubble shrinks to nothing because the surface tension of the liquid works against the repulsive force. Superfluid helium has very little surface tension, so the bubble can become much larger. The two opposing forces balance when the diameter of the bubble is about 40 angstroms – still far to tiny to see.


The researchers used a planar transducer – basically, a loudspeaker that produces flat, not focused, sound waves – to pummel the whole volume of liquid helium with sound. As each wave overtook an electron bubble, it alternately increased and decreased the surrounding pressure. Under negative pressure, the bubbles expanded to about eight microns, the size of a small speck of dust, then shrank again as the next wave of high pressure washed over them. A strobe light, synchronized to the sound pulse, illuminated the bubbles without overheating the chamber.


Running a camcorder in “super night mode,” Guo and Maris were able to record the approximately 2,000 photons they estimate were scattered by the expanded bubbles, producing a series of electron-bubble images on each frame of videotape.


“The results are very original and really spectacular,” said Sébastien Balibar, research director for physics at l’Ecole Normale Supérieure in Paris, “imaging single vortices of atomic size with a sound wave is an astonishing achievement.”


To be sure they were seeing electron bubbles and not just trapped dust, the researchers gradually increased the power to the transducer. They detected no points of light at low power and then a rapid increase in the appearance of bubbles at a particular voltage, just as their calculations predicted. Dust particles would exhibit no such threshold.


The researchers had planned to introduce streams of electrons into the chamber from a radioactive source, but found that even without a source, a number of electrons could be seen moving through the chamber. Most traveled in a fairly straight line leading away from the transducer, which produces a flow of heat down through the liquid.


A few of the electrons, however, followed a distinctly different snakelike path. Maris and Guo hypothesize that those electrons are following the lines of superfluid vortices – a phenomenon akin to a tornado in which the liquid spins at high velocity around a line. “The vortex is like a piece of string running through the liquid,” said Maris. “The electron bubble is attracted to the core of the vortex and gets attached to it. It’s as though it’s sliding down this rope that winds through the fluid.” By following the path that the electron takes as it slides along the vortex, the researchers were able to observe vortex lines for the first time. “People never thought it would be possible to visualize the vortex lines,” said Guo, “but then, almost by accident, we saw them.”


Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews and maintains an ISDN line for radio interviews. For more information, call the Office of Media Relations at (401) 863-2476.



######


Дизайн и программирование N-Studio 
А Б В Г Д Е Ё Ж З И Й К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Ъ Ы Ь Э Ю Я
  • Chen Wev .  honorary member of ISSC science council

  • Harton Vladislav Vadim  honorary member of ISSC science council

  • Lichtenstain Alexandr Iosif  honorary member of ISSC science council

  • Novikov Dimirtii Leonid  honorary member of ISSC science council

  • Yakushev Mikhail Vasilii  honorary member of ISSC science council

  • © 2004-2019 ИХТТ УрО РАН
    беременность, мода, красота, здоровье, диеты, женский журнал, здоровье детей, здоровье ребенка, красота и здоровье, жизнь и здоровье, секреты красоты, воспитание ребенка рождение ребенка,пол ребенка,воспитание ребенка,ребенок дошкольного возраста, дети дошкольного возраста,грудной ребенок,обучение ребенка,родить ребенка,загадки для детей,здоровье ребенка,зачатие ребенка,второй ребенок,определение пола ребенка,будущий ребенок медицина, клиники и больницы, болезни, врач, лечение, доктор, наркология, спид, вич, алкоголизм православные знакомства, православный сайт творчeства, православные рассказы, плохие мысли, православные психологи рождение ребенка,пол ребенка,воспитание ребенка,ребенок дошкольного возраста, дети дошкольного возраста,грудной ребенок,обучение ребенка,родить ребенка,загадки для детей,здоровье ребенка,зачатие ребенка,второй ребенок,определение пола ребенка,будущий ребенок