Broadband CARS Probe Using the Picosecond Continuum

Abstract

Coherent antistokes Raman scattering (CARS) provides a potentially useful diagnostic approach to the identification and study of transient molecular fragment species produced as the primary events in UV laser photolysis of molecules. GROSS, GUTHALS, and NIBLER [1] applied nanosecond dye laser techniques to obtain scanned as well as broadband single-shot CARS spectra of transient species from 266-nm photolysis of benzene vapor and derivatives. This work was extended to the picosecond time scale by HETHERINGTON III, KORENOWSKI, and EISENTHAL [2] who used optical parametric generation to provide tunable frequency Stokes pulses for a point-by-point probe of the photolysis spectrum. Earlier, GREEN, WEISMAN, and HOCHSTRASSER [3] had demonstrated single frequency picosecond CARS measurements in molecular nitrogen. In the present paper, development of a broadband picosecond CARS probe technique is reported. The method uses the picosecond white-light continuum [4] as Stokes light and enables an extensive antistokes spectrum to be obtained in a single 5-ps laser pulse.