The central CC bond stretch frequencies and structure of S 2 and S 1 diphenylacetylene in solution studied by picosecond time-resolved CARS spectroscopy

Abstract

Picosecond time-resolved CARS spectra of diphenylacetylene and its 13C species were reported. CARS bands due to two transient species with different lifetimes were observed. The short-lived species (lifetime < 20 ps) has been identified as the S 2 state and the long-lived species (lifetime ≈ 200 ps) as the S 1 state. The 2099 cm −1 band of the S 2 state has been assigned to the central CC bond stretch while the 1577 cm −1 and 1557 cm −1 bands of the S 1 state are assignable to the normal modes which contain contributions of the central CC stretch vibration. The bond order of the central CC part decreases markedly in the S 1 state.