Low-energy optical transitions in organic metal DMTSA-BF4

Low-energy absorption bands in the polarized reflection spectrum of metal-l ike DMTSA-BF4 (2,3-dimethyltetraselenoanthracene-BF4) were interpreted base d on a one-dimensional band theory using a point charge approximation, Drud e-like dispersion observed in the E parallel to c reflection spectrum was a ssigned to the intra-band transition along the conducting axis. A broad abs orption band at ca. 6900 cm(-1) in the E perpendicular to c reflection spec trum was assigned to the inter-branch transition from the lower to the uppe r branch produced by folding the HOMO band at the zone boundary. The transi tion probability of this electronic transition originated from the zigzag s tacking structure of DMTSA molecules in this crystal, The calculation of th e conductivity spectra of this transition according to this proposal agrees well with the observed conductivity spectrum. (C) 1999 Elsevier Science Lt d. All rights reserved.