Mode-specific intermolecular vibrational energy transfer. II. Deuterated water and potassium selenocyanate mixture

Vibrational energy transfer from the first excited state (2635 cm-1) of the O-D stretch of deuterated water (D₂ O) to the 0-1 transition (2075 cm-1) of the CN stretch of potassium selenocyanate (KSeCN) in their 2.5:1 liquid mixture was observed with a multiple-mode two dimensional infrared spectroscopic technique. Despite the big energy mismatch (560 cm-1) between the two modes, the transfer is still very efficient with a time constant of 20 ps. The efficient energy transfer is probably because of the large excitation coupling between the two modes. The coupling is experimentally determined to be 176 cm-1. An approximate analytical equation derived from the Landau-Teller formula is applied to calculate the energy transfer rate with all parameters experimentally determined. The calculation results are qualitatively consistent with the experimental data.