Posts Tagged ‘photoemission’
Nano-Miniaturization Technique Developed for Rocketry Leads to Better Dentistry
The technique uses a tiny energy into visible light, which provides much more detail and higher contrast. A Swedish firm called Scint-X used structured silicon to make the scintillator, aiming to improve its resolution.
Scintillators produce light by activating an alkali halide crystal — like table salt, or in this case, cesium iodide — and adding a slight chemical impurity. Reactions then occur at atomic scales and produce light through the emission of electrons (the photoelectric effect). A CCD imager or another device captures that light.
Resolution has been a problem in previous scintillators, however. Scint-X produced their scintillator in structured silicon, and asked the Swedish firm Nanospace to make it in their high-precision facility.
Nanospace made a matrix in the silicon by etching narrow channels and then filling them with a cesium iodide scintillator material, made impure by the addition of thallium. When X-rays enter the channels, they are converted into green light, as . The light is reflected off the channel walls and then picked up by a CCD chip.
The camera’s resolution is better than five microns, according to the ESA. Even better, the X-ray unit inserted into a dental patient’s mouth is much thinner than existing models, and thus more comfortable.
Incidentally, Nanospace has already used this production method to cut the world’s smallest rocket motor from silicon wafers. The Swedish Prisma satellite, which measures just 2 inches by 1.7 inches, is a complete micro-propulsion system, according to the ESA. It launched in June.
Nanospace is working with the European Space Agency to provide miniaturized thrusters for future spacecraft. The scintillator camera will also be used to study the melting and solidification of metals in space, according to Scint-X.
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German Scientists Measure How Fast an Electron Jumps, the Shortest Time Interval Ever Measured
During photoemission – the expulsion of electrons from an atom by bombarding them with high-energy light – it’s always been assumed that there is no delay between the photons’ impact and the breaking loose of the target electron. But a group of German researchers in collaboration with Greek, Austrian, and Saudi Arabian colleagues decided to challenge that assumption with extremely sensitive time measurement tech.
The team bombarded atoms of neon gas with near-infrared laser light in 10-15 second pulses and ultraviolet pulses of far shorter durations of just 180 attoseconds (remember, an attosecond is one billionth of one billionth of one second). The near-IR light served as an attosecond chronograph, measuring the time of UV impact and the time the electrons exited their orbits.
Their findings turned up two interesting results. For one, they found that electron ejection is not a “time zero” action as once presumed, but that excited electrons hesitate very, very briefly before leaving the atom. But perhaps more interesting, they found that electrons from different orbitals behaved differently, leaving the atom at slightly different times even though they were impacted simultaneously.
The researchers are not exactly sure why this is, but it likely has to do with some small, overlooked influence that electrons exert over one another that is different that the forces exerted on electrons by their nuclei. If that’s the case, the tiny time lag could have big consequences for physics, a discipline ruled by the interactions between atoms and the behavior of electrons. Until they figure all that out, they can at least take pride in their 20-attosecond record for the shortest time interval ever directly measured.
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