Optical Properties of Hexamethylene-Tetraselenafulvalinium Tetracyanoquinodi-Methanide (HMTSF-TCNQ)

Polarized single crystal reflectance studies of HMTSF-TCNQ are presented. One reflectance component perpendicular to the highly conducting direction is flat and rather low, the other shows a transition at ohgr = 16000 cm–1, much stronger than usually seen in conducting TCNQ salts. The highly conducting direction displays a plasma edge. An analysis yields a plasmon frequency ohgrp = 7400 cm–1, an inverse life time lambda = 1300 cm–1, and an optical mass m* = 1.9 mo. The low-temperature reflectance gives ohgrp = 8200 cm–1 and a 2.4 times longer lifetime, consistent with the temperature dependence of the do conductivity.