X-ray excited optical luminescence (XEOL) detection of x-ray absorption fine structure (XAFS)

Abstract

The x-ray excited optical luminescence (XEOL) from a variety of rare-earth ions was used as a detection mode for the collection of L-edge x-ray absorption fine-structure (XAFS) data. In order to understand the source of the observed optical signal, advantage is taken of the known luminescent response of f ions in a variety of transparent host materials. Whereas some samples exhibit an optical response that is indistinguishable from the transmission XAFS data, other samples show marked differences between the data obtained with the two different detection schemes. The unexpected optical luminescence of a Gd2O3 sample is traced to a Eu impurity. An optical spectrum of 0.4% Tb in Gd2O2S, excited by x-ray photons at the Gd edge, is used to demonstrate that the optical signal may arise from an ion different from the absorbing ion. The implications of this energy transfer are discussed in terms of the suitability of XEOL as a detection scheme for XAFS spectroscopy.