Fifth-order two-dimensional Raman spectra of CS2 are dominated by third-order cascades

We have demonstrated that fifth-order stimulated Raman spectra of the inter molecular modes in CS2 are dominated by cascading third-order processes. Pr evious studies have successfully discriminated against a sequential cascadi ng process, but did not account for parallel third-order cascades. All of o ur measured spectra were successfully simulated considering only cascades b uilt directly from our measured third-order spectra. Using an appropriately chosen phase matching geometry we also measured the sequential cascade, wh ich should exist with equal probability to the parallel cascade. When emplo ying a phase matching geometry that provided substantial discrimination aga inst all of the third-order cascades we were not able to measure any signal . We assign an upper limit for the true fifth-order signal of 2% of the cas caded signal. (C) 1999 American Institute of Physics. [S0021-9606(99)00131- 2].