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Equilibrium structure of CO+ from its millimeter wave spectrum. Breakdown of the Born–Oppenheimer approximationa)
Microwave transitions of CO+ have been observed for several isotopic substitutions, in different vibrational states: 12C 16O+(v=0,1,2,3,4), 12C 18O+(v=0,1), 13C 16O+(v=0,1), and 13C 18O+(v=0). All mea...
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Nonadiabatic approach for resonant molecular multiphoton absorption processes in intense infrared laser fields

J. Chem. Phys. 79, 4708 (1983); doi:10.1063/1.445612

Issue Date: 15 November 1983

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Tak-San Ho and Shih-I Chu
Department of Chemistry, University of Kansas, Lawrence, Kansas 66045
A nonperturbative approach for efficient and accurate treatment of the molecular multiphoton absorption (MPA) quantum dynamics in intense infrared (IR) laser fields is presented. The approach is based on the adiabatic separation of the fast vibrational motion from the slow rotational motion, incorporating the fact that the IR laser frequency is close to the frequencies of adjacent vibrational transitions. One thus first solves the quasivibrational energy (QVE) states (or, equivalently, the dressed vibrational states) with molecular orientation fixed. This reduces the computationally often formidable (vibrational-rotational) Floquet matrix analysis to a manageable scale, and, in addition, provides useful physical insights for understanding the nonlinear MPA dynamics. The QVE levels are found to be grouped into distinct energy bands, characterized by the IR frequency, with each band providing an effective potential for molecular rotation. Whereas the interband couplings are totally negligible, the intraband nonadiabatic angular couplings are the main driving mechanisms for inducing resonant vibrational–rotational multiphoton transitions. The utility of the method is illustrated by a detailed study of the sequential MPA spectra for 12C 16O molecule, including state-to-state multiquantum transitions and transitions from initially thermally distributed states as a whole. Results are presented for the case of IR laser intensity 50 GW/cm2 and frequencies ranging from 2115 to 2165 cm−1. Excellent agreement of the MPA spectra obtained by the nonadiabatic approach and the exact Floquet matrix method was observed in all fine details. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.
History: Received 14 July 1983; accepted 9 August 1983
Permalink: http://link.aip.org/link/?JCPSA6/79/4708/1
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KEYWORDS and PACS

Keywords
PACS
  • 33.80.Kn
    Molecular spectra and interactions of molecules with photons Photon interactions with molecules Multiphoton processes
  • 33.20.Ea
    Molecular spectra and interactions of molecules with photons Molecular spectra, grouped by wavelength ranges Infrared spectra
  • YEAR: 1983

PUBLICATION DATA

ISSN:
0021-9606 (print)   1089-7690 (online)
Publisher:
AIP is a member of CrossRef AIP

REFERENCES (15)
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