Energy photons and

Spectroscopic techniques can be carried out in situ (low-energy photon, etc.) and ex situ or in vacuo (high-energy photon and electron techniques). Ex situ microscopic techniques have been employed for many years to examine surfaces, and are now widely used tools. However, in situ microscopic techniques with resolution approaching the atomic scale... 

Proceeding in parallel with XPS was the development of ultra violet photoemission spectroscopy (UPS) (2). This technique exploits low energy photons and must be confined to studies of electron states rather near the Fermi level (Ep). For investigating occupied electron states in the vicinity of Ep, UPS and XPS can serve as excellent complementary spectroscopies. 

It is for this reason that quantum efficiency does not usually exceed 100%. There are, however, some phosphors which absorb a high energy photon and then emits two photons. However, the efficiency does not exceed 100%. Only 1 or 2 phosphors have been said to have an efficiency of 100% but in view of the above discussion, there is some doubt as to the accuracy of the measurements. 

Recently it has been shown (36) that electron-beam irradiation of styrene-vinyl ketone copolymers show higher yields of type-I radicals than expected from UV photolysis measurements. It seems clear that some part of the excess energy of high-energy photons and electrons is imparted to the translation kinetic energy... 

Fig. 1 In stacked nnultijunction solar cells, the top cell converts higher energy photons and transmits the remainder onto layers, each of smaller band gap cell than the layer above, for more effective utilization of the solar spectrum.

Generator-derived therapeutic radionuclides have a number of characteristic decay processes, and can emit P particles. Auger electrons, low-energy photons, and a particles. Since many therapeutic radionuclides are characterized by P decay, they are often directly produced in a nuclear reactor, since neutron capture by the target nuclide forms a radioactive or unstable product that decays by P emission. Key examples of therapeutic radionuclides obtained from reactor-produced parent radionuclides include Ho - from the Dy/ Ho generator, and Re - from the W/ Re generator. 

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