Femtosecond electronic dephasing in large molecules in solution using mode suppression

Abstract

The femtosecond electronic dephasing of large molecules in solution is measured using a three-pulse photon echo mode cancellation technique. We have demonstrated the suppression of the quantum interference in the echo decay caused by the dominant ring breathing mode at 590 cm −1 found in oxazine dyes. We have calculated the echo decay including the entire manifold of vibronic levels and have determined the dephasing time T 2 to be in the range of 30 to 70 fs for the dye molecules nile blue and LD690.