High-resolution spectroscopy of matrix-isolated ReO_4^− molecules

Abstract

The temperature-dependent linewidth of the saturable infrared active ν3 vibrational mode (10.8 μm) of ReO4− molecules in pure-KI host crystals has been measured between 2 and 600 K. Below 20 K the absorption line is inhomogeneously broadened and has a 0.016-cm−1 width (FWHM). Above 30 K the transition is homogeneously broadened by elastic acoustic phonon-scattering processes. The low-temperature inhomogeneous width of ReO4− molecules in KI:RbI alloys is 2 orders of magnitude larger than for the pure KI crystal, and the absorption is coincident with the 10.8-μm P(42) CO2 laser line at all temperatures.