THE ABSORPTION SPECTRUM OF THE LOWEST TRIPLET STATE IN CRYSTALLINE TRANS-STILBENE

Author Institution: Department of Chemistry, National Taiwan UniversityThe absorption spectrum of the lowest triplet state of trans-stilbene is observed between 14 kK and 18 kK in a crystal 4 cm long cooled to $4.2^{\circ}K$. The spectrum shows the following properties of trans-stilbene in the lowest triplet state: 1. The oscillator strength is $(3\pm2)\times10^{-9}$, which is about an order of magnitude larger than the triplets in ordinary aromatic compounds. Most of the intensity is induced vibronically by an out-of-plane vibration. 2. Seven normal modes in the triplet are identified in the spectrum. 3. Lines in the spectrum are broad (8 K), probably due to unresolved exciton structures