Singlet—Triplet Exciton Absorption Spectra in Naphthalene and Pyrene Crystals

Abstract

Singlet—triplet exciton absorption spectra have been measured in naphthalene and pyrene single crystals at room temperature by observing the dependence of the ``anti-Stokes'' emission intensity resulting from mutual annihilation of triplet pairs on the wavelength of exciting light. The origin of the naphthalene spectrum is at 21 170 cm−1, and the most prominent intervals in the vibrational structure are 490 and 1360 cm−1. The origin of the pyrene spectrum is at 16 850 cm−1, and the vibrational structure for the lowest triplet state in this crystal includes the intervals 410, 1210, 1380, and 1590 cm−1.