S1(n, π∗), 1A2 fluorescence and T1(n, π∗), 3A2 phosphorescence spectra of xanthone vapor

Emission spectra of xanthone vapor have been measured at different temperatures along with the excitation and absorption spectra. Fluorescence from the S1(n, π∗), 1A2 and phosphorescence from the T1(n, π∗), 3A2 states were separated to extract only the fluorescence spectrum. The vibrational structure of the fluorescence was interpreted in terms of the CO stretching mode and the modes combined with the CO stretching, showing a maximum near 24 000 cm−1. The locations of the S1 and T1 origins are observed at 26 940 and 25 700 cm−1, respectively. Analysis of the data includes the determination of the vibrational frequencies in the fluorescence and phosphorescence.