High-resolution core level photoelectron spectra of solid TCNQ: determination of molecular orbital spatial distribution from localized shake-up features

Abstract

High energy resolution X-ray photoelectron spectra of the N 1s and C 1s core levels of solid tetracyanoquinodimethane (TCNQ) are presented. The N 1s binding energy is determined to be 399.7 eV. A single shake-up satellite is detected 2.6 eV to higher binding energy in the N 1s spectrum. The C 1s spectrum shows two core features and a single shake-up satellite. The C 1s shake-up feature is associated with core ionization of the carbons external to the ring and allows determination of the spatial extent of the highest occupied and lowest unoccupied molecular orbitals of TCNQ. This data indicates that the orbitals involved in charge-transfer compound formation are located near the cyano ends of the molecule.