Electromagnetic Production Of Electron Pulses

When a small metallic tip in the nanometre range is excited by incident laser pulses of very short interval electrons are given off as would be expected. Due to the slightly strange nature of the excitation this method produces slightly different results than the photoelectric effect. As the electromagnetic field magnitude increases on the surface of the metal electrons begin to tunnel right out of the metal rather than just be excited to the surface. This can lead to the emitted electrons forming coherent waves that can demonstrate various quantum phenomenon. As the laser intensity is ramped up and up the effective current produced by these moving electrons also increases. At high currents, many electrons are released per pulse of laser light. Just before the energy given is enough that the electrons can begin to escape by tunnelling; some electrons that would be emitted get forced back into the metal and then get released after a few moments with a loss of energy, some do not even make it back out and it can be assumed they were scattered so much as to lose the energy required to escape. It is believed this effect is caused by the oscillating nature of the electromagnetic field although there is a clear point where the laser goes from producing weak to strong electric field. The weak never causes the effect and the strong rarely doesn’t. The ability to produce pulsed emission of electrons is important for various experimental and imaging techniques, understanding when and why strange anomalies occur makes these applications more viable and reliable.


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