Picosecond Time-Resolved Raman/Coherent-Raman Spectroscopy Using the “Pico-Pump and Quasi-CW Probe” Method with a Streak Camera

Abstract

A Picosecond time-resolved spontaneous Raman measuring system using a streak camera was constructed. Nanosecond probing laser pulses were used with picosecond UV pumping. Raman scattering at each delay time was time-resolved and detected by a streak camera. Two dimensional (the time and the frequency domain) simultaneous detection of Raman scattering has been carried out. Time-resolved Raman spectra of benzophenone at delay times ranging from −1.25 ns to 1.5 ns were obtained with one single measurement. A picosecond time-resolved multiplex CARS measuring system based on the same principle was also constructed. Nanosecond narrow band laser pulses and broad band dye laser pulses were used as CARS probing ω₁ and ω₂, respectively, with the picosecond UV pumping pulses. The cis-trans photoisomerization dynamics of all-trans and 9-cis retinal was investigated. It was clarified that the conformational change from the 9-cis form to the all-trans takes about 880 ps in the triplet manifold.