Microcharacterization of spectral memory materials using nuclear forward scattering

Abstract

In the past europium doped materials have been tailored in our group, which could exhibit the highest spectral storage densities known to date. In these materials, europium exists in both doubly and triply ionized states. Therefore, it is necessary to control the relative concentration of Eu 2+ and Eu 3+ . Due to accidental overlap of Eu 2+ and Eu 3+ optical transitions in this medium optical spectroscopy cannot be used to determine their relative concentration. For highly enriched europium samples, such a ratio can be determined by Mossbauer spectroscopy. However, at very low concentrations of the order of 0.01% of Eu in MgS that are necessary for these materials, conventional Mossbauer spectroscopy requires prohibitively long data acquisition times. In this article, we present and compare the ways of solving this problem with conventional and the time domain Mossbauer spectroscopy using Nuclear Forward Scattering. The synchrotron of the Advanced Photon Source at Argonne National Laboratory has been used as the source of high intensity, coherent and monochromatic gamma rays in NFS experiments. It is shown that in time domain Mossbauer spectroscopy the data acquisition times can be reduced by two orders of magnitude or more. This is of paramount importance for Mossbauer spectroscopy of very small samples or the samples with very low concentrations of the active isotope.