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Electron in Motion
An electron rides on a light wave after just having been pulled away from an atom. Credit: Lund University
Scientists have filmed an electron in motion for the first time, using a new technique that will allow researchers to study the tiny particle's movements directly.
Previously it was impossible to photograph electrons because of their extreme speediness, so scientists had to rely on more indirect methods. These methods could only measure the effect of an electron's movement, whereas the new technique can capture the entire event.
Extremely short flashes of light are necessary to capture an electron in motion. A technology developed within the last few years can generate short pulses of intense laser light, called attosecond pulses, to get the job done.
"It takes about 150 attoseconds for an electron to circle the nucleus of an atom. An attosecond is 10-18 seconds long, or, expressed in another way: an attosecond is related to a second as a second is related to the age of the universe," said Johan Mauritsson of Lund University in Sweden.
Using another laser, scientists can guide the motion of the electron to capture a collision between an electron and an atom on film.
The length of the film Mauritsson and his colleagues made corresponds to a single oscillation of a wave of light . The speed of the event has been slowed down for human eyes. The results are detailed in the latest issue of the journal Physical Review Letters.
Length: 72
Rating: 4.50 (56 ratings)
Tags: electronics science atom electron education
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Electron Diffraction to Tchaikovsky Waltz of the Flowers
Did this about 10 years ago for my physics degree final year project - numerical solutions to the time-dependent Schrödinger Equation (TDSE) applied to electron diffraction. Primarily we were interested in the effects of different slit geometries, as this had never been studied before (for example there's no way you could analytically solve Kirchoff's diffraction theory to anything other than 1-D slits, that is, slits without thickness and funny shapes) - all is performed in dimensionless units.
The electron is modelled here as a wavepacket, that is, a Gaussian distribution superimposed with a sinusoidal wave term, and it interacts in the TDSE with the potential boundary of a double-slit wall, I also investigated other potentials and confines, including an elliptical potential, which was an idea based on what was then a recent publication by IBM laboratories on their STM atom manipulation on substrates - in particular the Stadium Corral. I wanted to approximate the effect they observed with wave effects on the surface state electron density, with the peaks at the foci of the ellipse. They observed that an impurity at one focus led to the disappearance of the peak at the other focus, due to the wave nature to the electron distribution. I never quite got that far as it would have required a lot more computing power (and it was way beyond the objective of the project), but focusing of the electron packet can be observed.
The most advanced desktop PCs I had at my disposal were PII 300 MHz machines - I commandeered 4 machines in our IT room (which got me in trouble with IT dept for never logging out - I disabled their auto logout/reboot scripts which ran a disk cleaner, deleting all user files after midnight - they even blocked my account for a couple of days!) - these machines spent the next month solving the TDSE for a number of conditions via the predictor-corrector method, approximating the differential equations with finite steps, in good old Fortran. This method, however, results in two opposing initial directions for the wave packet to move in, hence the electron splits in two.
Time-dependence therefore suggests that the resulting data be presented in some sort of movie (though not just a movie - time averaged plots can and was also done besides this, for comparison with classical diffraction), so the final probability distribution data was then rendered frame by frame in Matlab. At that time Matlab was a bit basic, you couldn't automatically grab each frame and convert into a movie like you can now. Consequently each frame had to be manually saved as a bmp, all 7000 or so, then imported into some basic animation package, I forget what is is now. For a bit of fun I added the marvellous Waltz of the Flowers by Tchaikovsky. Nobody can write music like he did!
The "finé" at the end was a play on the French word for finished - "fini" - all the French people I knew / met at university seemed to say "é" at the end of everything!
Length: 335
Rating: 5.00 (2 ratings)
Tags: electron difrraction qauntum numerial computation time depedent Schroedinger Equation Tchaikovsky Waltz of the Flowers
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Cyanna - Electron
Greece - Cyanna (pronounced see-anna) is a powerful blend of rock n roll and electronic beats. Having won the Greece Coca-Cola Soundwave contest they were invited to play in the Coca-Cola Soundwave Tent at the Hurrican festival, Germany.
www.myspace.com/cyannamercury
Length: 333
Rating: 5.00 (11 ratings)
Tags: Cyanna electron cokemusic coca-cola soundwave alternative electronica
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RF electron source
Radio frequency (RF) plasmas are attractive as electron beam sources because they allow for a design where the cathode dose not participate in electron production while providing high efficiency and long life operation. Traditionally, hollow cathodes or tungsten filaments have been used as electron sources because of their high electron current density and relatively low power requirements. However, their operational lifetime is limited by cathode and filament deterioration, contamination, and barium diffusion rates, and in some cases requiring a large amount of inert feed gas, thus rendering them less suitable use in corrosive environments and sustained use.
The Non-ambipolar Electron Source (NES) is a device that produces electron beams from plasma created with RF fields in a magnetized plasma combined with electron extraction by electron sheaths.
Length: 113
Rating: 3.30 (14 ratings)
Tags: NES non-ambipolar electron source nonambipolar ambipolar rf radio frequency helicon inductive capacitive plasma wave
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