"Highly Selective Relaxation of the OH Stretching Overtones in Isolated HDO Molecules Observed by IR Pump-Repump-Probe Spectroscopy"D. Hutzler, J. C. Werhahn, R. Heider, M. Bradler, R. Kienberger, E. Riedle, and H. Iglev
J. Phys. Chem. A 119, 6831 - 6836 (2015).
A quantitative investigation of the relaxation dynamics of higher-lying vibrational states is afforded by a novel method of IR pump-repump-probe spectroscopy. The technique is used to study the dynamics of OH stretching overtones in NaClO4·HDO monohydrate. We observe a continuous decrease of the energy separation for the first four states, i.e. ν01 = 3575 cm-1, ν12 = 3370 cm-1 and ν23 = 3170 cm-1, respectively. The population lifetime of the first excited state is 7.2 ps, while the one of the second excited state is largely reduced to 1.4 ps. The relaxation of the v = 2 state proceeds nearly quantitatively to the v = 1 state. The new information on the OH stretching overtones demands improved theoretical potentials and modeling of the H bond interactions. This work shows the potential of the new technique for the precise study of complex vibrational relaxation pathways.
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