Structure of the S1 state of diphenylacetylene as studied by time-resolved CARS and infrared spectroscopy

Picosecond transient CARS and picosecond transient infrared absorption spectra of three isotope-substituted diphenylacetylenes (DPA, DPA-13C, and DPA-d5) in solution have been recorded. The recorded CARS and infrared spectra of the S1 state have been interpreted in terms of a three-coordinate normal coordinate analysis. Existence of a center of symmetry has been indicated from the mutual exclusion relationship established for the CARS and infrared spectra, strongly supporting a trans-bent structure of the S1 state.