The Absorption Spectrum of the Lowest Triplet State in Crystalline trans‐Stilbene

Abstract

The absorption spectrum of the lowest triplet state (T1*‐S0) of trans‐stilbene is observed between 14,000 and 18,000 cm−1 with a crystal four centimeters long, cooled to 4.2°.K. This transition is more intense (f=3×10−9) than the similar transition in anthracene, due to vibration‐induced spin‐orbital coupling. Vibrational structures in the spectrum are well resolved and seven frequencies are assigned to normal modes in the T1* state of trans‐stilbene. Exciton structures in crystal are not resolved.