Vibrational dephasing times of bis(dimethylamino)heptamethine iodide determined by CARS using incoherent light

Interferometric coherent anti‐Stokes Raman scattering (ICARS) using incoherent laser light was used for time‐resolved measurements of vibrational parameters of solutions of bis(dimethylamino)heptamethine iodide in the ground and the S1, state. The vibrations at 1124, 1195, 1285 and 1304 cm−1 have dephasing times in the range 0.3–1.1 ps. The shortest dephasing time is observed for the normal mode at 1195 cm−1 with a large amplitude for the N atoms. The coherence peak in the ICARS signal around zero delay is broadened due to coupling to the electronic transition. The same peak width of 80 fs is found using degenerate four‐wave mixing.