A steady-state rate equation inversion method for quantitative measurement of temperature-dependent absorption in strongly absorbing oxysalts

A steady-state rate equation-based inversion method was proposed to quantitatively obtain temperature-dependent absorption spectra of strongly absorbing solids without requiring a transmission path. By jointly analyzing the photoluminescence, photoluminescence excitation, and time-resolved spectra of CaMoO 4 and CaWO 4 , together with the Xe-lamp spectrum, the relative absorption cross sections ( σ rel ) of MoO 4 2− and WO 4 2− groups were derived over 173–373 K. The integrated σ rel of the MoO 4 2− groups increases nearly monotonically with temperature, in contrast to the thermal quenching behavior typically observed in conventional PLE spectra. This enhancement may be related to strengthened electron–phonon coupling and increased thermal population of ground state vibrational levels. A similar trend in CaWO 4 suggests that this phenomenon may be common among scheelite-type oxyanion compounds, providing a feasible approach for probing intrinsic absorption in strongly absorbing solids.