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Density evolution of the picosecond time‐domain CARS responses from carbon dioxide gas
Author(s) -
Morozov V.,
Mochalov S.,
Olenin A.,
Tunkin V.,
Kouzov A.
Publication year - 2003
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.1097
Subject(s) - dephasing , picosecond , relaxation (psychology) , collision , vibrational energy relaxation , atomic physics , chemistry , molecular physics , physics , optics , condensed matter physics , laser , computer science , psychology , social psychology , computer security , excited state
Results of a joint experimental and theoretical study of CARS transients produced by picosecond two‐color pumping of the CO 2 Q‐branch at 1285 cm −1 are reported. The coherence decay patterns recorded in a wide dynamic range (3–8 decades) and in a broad gas density interval (ρ = 0.02–20 amagat) made it possible to track different channels of collision‐induced relaxation. The undertaken signal simulations account for the finite pump–probe pulse durations and also for the collision‐perturbed Doppler effect, vibrational dephasing and collisional mixing of rotational states. The last effect was tackled by applying the quantum fast‐collision model of rotational relaxation. Our recent data on the other Fermi‐dyad component at 1388 cm −1 were also simulated in the same way to derive a set of optimized relaxation rate parameters. New features revealed at low densities are ascribed to interference between the velocity and rotational relaxation channels. Copyright © 2003 John Wiley & Sons, Ltd.