Enhancement of vibrational coherence by femtosecond degenerate four-wave-mixing for a chromophore in 1-propanol glass

Abstract

The enhancement effect of vibrational coherence by femtosecond degenerate four-wave-mixing (DFWM) technique was investigated with a dye, NK-2990, doped in low temperature 1-propanol glass. The strongest enhancement was observed with the delay between the first and the second pulses, t₁₃, set at about quarter of the oscillation period, which does not coincide with the theoretical prediction of half the period. One of the enhanced vibrational modes at ca. 90 cm⁻¹ became significantly broader below the glass transition temperature, indicating its sensitivity towards microscopic viscosity of the environment.