Abstract

Few problems have attracted so much interest of picosecond spectroscopists as the photoisomerization of cis- and trans-stilbene.¹ Femtosecond transient absorption^1,2 and multi-photon ionization³ experiments have shown that in solution cis-stilbene S₁ state decays in ~1.4 ps independent of solvent temperature and friction. This decay process has been attributed to rapid torsion around the central C = C bond to the 90° twisted geometry which is thought to be the common intermediate for both cis- and trans-stilbene S₁ state decay, and has historically been designated as the "phantom state.^1-3. However, another isomerization channel, the dihydrophenathrene formation occurs with as high as 30 % quantum yield.⁴ In order to establish the mechanism for cis-stilbene non-radiative decay, and to investigate the role of the phantom state in cis-trans isomerization, this paper presents preliminary measurements of cis-stilbene dynamics in rare gas clusters that are formed by supersonic expansion.

© 1990 Optical Society of America