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Quantitative estimation of collisional dephasing rate in the X 1 A 1 – A 1 A 2 (4 1 0 ) band of formaldehyde with degenerate four wave mixing spectroscopy
Author(s) -
Carpanese M.,
De Dominicis L.,
Fantoni R.
Publication year - 2007
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1693
Subject(s) - dephasing , excited state , atomic physics , spectroscopy , chemistry , population , relaxation (psychology) , coherence (philosophical gambling strategy) , degenerate energy levels , physics , analytical chemistry (journal) , quantum mechanics , psychology , social psychology , demography , chromatography , sociology
The application of degenerate four wave mixing (DFWM) spectroscopy to the study of collisional dephasing in the 1 A 2 (4 1 0 ) excited band of formaldehyde has been carried out. The method relies on the measurement of DFWM signal dependence on the partial pressures of different buffer gases and in the saturated regime. Experiments were conducted with CO 2 , N 2 and He as colliding partners to H 2 CO, and collisional dephasing rates γ pd of the order of 10 10 s −1 atm −1 were estimated. The experimental findings clearly indicate that coherence decay is the dominant mechanism, with respect to rotational energy transfer (RET), in determining the DFWM signal decreasing with pressure. The comparison between the different values of γ pd measured and the literature data for γ RET has been used to shed light on key factors mostly ruling the competition between decoherence and population relaxation effects. Copyright © 2007 John Wiley & Sons, Ltd.