Picosecond dephasing times of HCl:Ar mixtures investigated by transient IR spectroscopy
✍ Scribed by H.-J. Hartmann; H. Schleicher; A. Laubereau
- Publisher
- Elsevier Science
- Year
- 1985
- Tongue
- English
- Weight
- 431 KB
- Volume
- 116
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
A recent technique involving coherent propagation of infrared picosecond pulses is applied to various rotation-vibration transitions of HCl : Ar (R-branch)_ Ultrafast dephasing and beating of the two HCI isotopes is directly measured at several bar total pressure and compared with spectroscopic and theoretical data. in the past decades valuable information on molecular dynamics in gases was obtained by several spectroscopic techniques, e.g_ conventional infrared absorption and Raman spectroscopy [I?_] _ Numerous investigations have been performed studying the effect of intermolecular interactions on the spectral linewidth (pressure broadening). More recently investigations of coherent light-matter interaction in the time rather than the frequency domain have opened the field of direct measurements of molecular time constants [3] (for a review, see ref_ [43)_ For gases at pressures around 1 bar the relaxation processes often proceed on the time scale of hard-core collisions of lo-lo s. As a consequence the use of coherent effects was made difficult by the necessarily high time resolution of subnanoseconds or shorter and corresponding intensity requirements [S] . Recently a novel time-resolved infrared spectroscopy was reported based on the coherent propagation of low-intensity picosecond pulses [6--81. For moderately short samples nearly free induction decay (NFID) of the resonantly interacting molecules was observed which provides direct information of the dephasing time T2 of the investigated rotation-vibration transition [S] . For longer samples, which are experi-