Ce. Mungan et al., INFRARED-SPECTROSCOPY OF THE STRETCHING MODES OF SEH- AND TEH- IN KCLAND KBR, Journal of physics and chemistry of solids, 56(5), 1995, pp. 735-743
The fundamental stretching modes near 4.5 mu m of SeH- and TeH- doped
in KCI and KBr are measured at high resolution at 1.7 K. For the KCl-d
oped samples, prepared by adding elemental Se (Te) to the melt and gro
wing under H-2, the concentrations of atomic Se (Te) are determined by
neutron activation analysis. An IR/Raman/UV spectroscopic survey of i
mpurities in these crystals indicates that Se(Te) is present mainly in
the form of SeH-(TeH-). Thus, ratioing the vibrational absorption str
engths to the atomic concentrations gives the integrated cross-section
s of SeH-(TeH-), equivalent to an effective charge q of similar to 0.
14e and a radiative lifetime of similar to 30 ms. This value of q is
much smaller than theoretical predictions for the free ions, implying
a matrix-induced screening of the dipole moment. The lowest-order mech
anical anharmonic correction to the vibrational frequencies is found t
o be similar to 2% by measuring the first overtones and is used to fit
the isotopic shifts in the spectral peaks. These peaks are homogeneou
sly broadened at 1.7 K; if lifetime limited, this implies a vibrationa
l relaxation of the order of 100 ps, nine orders of magnitude faster t
han the radiative lifetime.