Berlin 2001 – scientific programme
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MO: Molekülphysik
MO 10: Spectroscopy I: Ultra-short Time Spectroscopy
MO 10.2: Talk
Thursday, April 5, 2001, 16:00–16:15, H1058
Sub-picosecond IR-Spectroscopy of water: local structures and spectral relaxation — •Konstantinos Simeonidis and Robert Laenen — Technische Universitaet Muenchen, Physik-Department E11, James-Franck-Strasse, D-85748 Garching
The spectral substructure of the OH-stretching band of the isotopic mixture HDO in D2O is demonstrated in the temperature range from 273 K to 343 K, using 2-colour IR spectroscopy with tunable sub-picosecond pulses. From time-resolved spectra we derive four major spectral components peaked between 3330 and 3540 cm−1. Two components are related to local structures of water while the other two may be identified as combination modes between the hydroxilic stretching vibration of a preferred structure and a low-frequency hydrogen bridge bond vibration. One of the spectral components is assigned to water molecules in local hexagonal structures and a high frequency component to weakly bonded HDO molecules with probably bifurcated H-bonds. The measured cross relaxation among the spectral species hints towards a structural relaxation time of 1.5 to 0.8 ps in the range 273-343 K. The population lifetime in the first excited state of the OH-stretching vibration at the peak of OH-band is determined to be 1.1± 0.2 ps at room temperature.