title: Phase-matching and dilution effects in two-dimensional femtosecond stimulated Raman spectroscopy.
abstract: We present theoretical and experimental data for the attenuation of the cascade signal in two-dimensional femtosecond stimulated Raman spectroscopy (2D-FSRS). In previous studies, the cascade signal, caused by two third-order interactions, was found to overwhelm the desired fifth-order signal that would measure vibrational anharmonic coupling. Theoretically, it is found that changing the phase-matching conditions and sample concentration would attenuate the cascade signal, while only slightly decreasing the fifth-order signal. By increasing the crossing angle between the Raman pump and probe and the impulsive pump and probe, the phase-matching efficiency of the cascade signal is significantly attenuated, while the fifth-order efficiency remains constant. The dilution experiments take advantage of the difference in the concentration dependence for the fifth-order and cascade signal, in which the fifth-order signal is proportional to concentration and the cascade signal is proportional to concentration squared. Experimentally, it is difficult to see a trend in the data due to instability in signal in the phase-matching experiments and lack of signal at low concentrations in the dilution experiments.
authors.affiliation: Department of Chemistry, University of Rochester, 120 Trustee Rd., Rochester, New York 14627, USA.
authors.forename: Barbara
authors.initials: B
authors.lastname: Dunlap
authors.forename: Kristina C
authors.initials: KC
authors.lastname: Wilson
authors.forename: David W
authors.initials: DW
authors.lastname: McCamant