Pressure dependence of the polarized reflectance spectrum of the solid charge-transfer complex, perylene-TCNQ: Estimation of microscopic parameters

The polarized reflectance spectrum of the perylene TCNQ complex has been measured at high pressure up to 27 kbar using a diamond anvil cell incorporated into a microspectrophotometer. The degree of charge transfer (ρ), the transfer integral (t), and the site‐energy difference (Δ) are estimated at each pressure from analysis of the charge‐transfer band. The pressure dependences of t and Δ are found to be ∂ ln t/∂P=+2.3% kbar 1 and ∂Δ/∂P= 6.4 MeV kbar 1, respectively. It is shown that the observed pressure dependence of the stabilization energy of the charge‐transfer excited state is mainly attributable to the change in the electrostatic energy accompanying the lattice contraction