VIBRATIONAL AND ELECTRONIC-SPECTRA OF MATRIX-ISOLATED PENTACENE CATIONS AND ANIONS

Pentacene cations and anions have been formed by electron bombardment of a vapor phase mixture of pentacene, Ar and CCl4 and trapped in an a rgon matrix. The electronic and infrared spectra of both ions have bee n recorded. Increasing concentrations of CCl4 resulted in the eventual disappearance of the anion spectrum. The intensity distributions of t he IR spectra of the ions are similar but differ markedly from the dis tribution of neutral pentacene. The ion intensities resemble the distr ibution of the so-called interstellar 'unidentified infrared' bands. T he visible bands of neural, cationic and anionic pentacene are compare d with the diffuse inters tellar bands.