Pressure Dependence of Absorption Edge, Luminescence Peak and Raman Frequency in Wolffram's Red Salt

Abstract

Absorption, luminescence and Raman spectra are studied under high pressure in Wolffram's red salt. It is suggested that the quasi-one-dimensional electron-phonon system is continuously changed by pressure from a moderate coupling state at atmospheric pressure to a weak coupling state, not by decreasing the electron-phonon coupling energy, but by increasing the transfer energy. The decrease of the phonon energy of the symmetric stretching vibration of Cl around Pt IV and the rapid decrease of the energy gap with the pressure increase up to 0.2 GPa are thought because the Pt IV -Cl distance would increase with increasing pressure as the Pt IV -Pt II distance decreases.