Pressure effects on the absorption spectra of KBr:Ag+

Abstract

Absorption bands A, B, and D in KBr:${\mathrm{Ag}}^{+}$ have been investigated under hydrostatic pressure at low temperature. The pressure shifts of these bands at 85 K are A: 5.093+0.14p-0.012${\mathit{p}}^{2}$ eV, B: 5.343+0.05p+0.006${\mathit{p}}^{2}$ eV, and D: 5.882+0.13p-0.016${\mathit{p}}^{2}$ eV, where pressure p is given in GPa units. The absorption intensity decreases and the half width becomes narrower under higher pressure. The pressure dependence of the peak position is analyzed by taking into consideration the ligand field interaction in addition to Drickamer's framework. The rather large blue shift is attributed to the enhancement of the ligand field under pressure, and the different shift rate (0.08\ensuremath{\sim}0.09 eV/GPa) between the A(D) and B bands results from the ligand field splitting of the d electron. It is suggested that the adiabatic potential in the excited states is deformed in Q(${\mathit{T}}_{1\mathit{u}}$) space. The changes of adiabatic potential in both the configuration coordinates of Q(${\mathit{A}}_{1\mathit{g}}$) and Q(${\mathit{T}}_{1\mathit{u}}$) are discussed.