Angular and energy distributions of low energy electrons in backscattered-Mössbauer spectroscopy

Abstract

The angular and energy distributions of resonant and nonresonant electrons below 50 eV have been investigated during backscattered conversion electron Mössbauer spectroscopy (CEMS). Reasonable consistency is achieved between theoretical predictions and experimental studies. Relatively few resonant or nonresonant electrons are observed/predicted between 600 eV and 50 eV, while a significant fraction of the total electron signal emerges below 50 eV. The low energy signal is shown to result from low energy Auger cascades, low energy shake-off electrons and secondary electrons attributed to higher energy events. Despite the presence of secondary electrons, the signal arising from low energy Auger and shake-off electrons can be used to discriminate those resonant electrons (i.e., resonant spectra) arising from the topmost 1.0 nm of the absorber. The relatively large number of low energy electrons permits relatively short acquisition times (ca. 1 h) and enhanced surface sensitivities. They may be especially useful in future depth-deconvolution efforts.