Properties of simple alkali-tetracyanoquinodimethan (TCNQ) salts. II. Optical properties of M^{+}TCNQ^{-} salts

Abstract

The interpretation of properties of (1:1) alkali-tetracyanoquinodimethan (TCNQ) salts on a one-dimensional Bloch model can be extended to optical spectra. Electronic absorptions in the spectral range of 4000-20 000 ${\mathrm{cm}}^{-1\mathrm{}}$ are interpreted as band-to-band transitions. These (split) bands are contructed from the ground-state and excited-state wave functions of the TCN${\mathrm{Q}}^{-}$ ion. A splitting in the absorptions arises from the variable density of states in an energy band. The polarized absorption spectra of KTCNQ were "calculated," using some basic assumptions, and compared with experimental data.