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Physics Colloquium – Seth Putterman
October 15, 2018 | 4:00 pm - 5:00 pm
Title: X-Ray Triboelectrification
Abstract: Triboelectrification – the transfer of charge between dielectric surfaces brought into and out of contact – is perhaps the longest standing unsolved mystery of the physical world. The unbalanced surface charge density regularly reaches 10^12 fundamental units/square-centimeter which corresponds to a nearby field of about a million volts/cm. The resulting discharges can generate x-ray pulses, whose duration is measured in nanoseconds, and which have sufficient flux to take x-ray photos. At least three independent processes can all work together in a sub-mm region to facilitate x-ray triboluminescence; 1) contact electrification; 2) surface conductivity and 3) a discharge that leads to Bremsstrahlung x-rays. To this day no one has designed the experiment which shows whether contact electrification is due to electrons going from surface “A” to surface “B” or ions going from “B” to “A”. Furthermore, there is no “ab-initio” theory of charge exchange between 2 incommensurate contacting surfaces. To drive such a theoretical effort, we present data on X-Ray emission from tapping of single crystals.