Infrared and visible luminescence spectra of TcCl 2–6 and TcBr 2–6 in cubic crystals

Abstract

The high-resolution infrared and visible luminescence spectra of TcCl^2–₆ and TcBr^2–₆ in several colourless cubic host crystals and of TcCl^2–₆ and K₂PtCl₆ and Cs₂TeCl₆ have been measured between 15 000 and 3500 cm^–1 at temperatures down to 10 K. Five electronic transitions involving the four lowest components of the t³_2g configuration have been assigned, each showing detailed vibronic structure. Analysis of the structure of the visible emission enables the presence of progressions in ν₁ but not in ν₂ to be identified. This is interpreted as indicating that the luminescence arises from the Γ₇ component of the ²T_2g excited state, although the two spin–orbit components are close together in these compounds. For TcBr^2–₆ in Cs₂TeCl₆ and K₂PtCl₆ the excited states are populated by energy transfer.