Resonance enhanced two-photon dissociation of H sub 2 by the X r arrow ( EF + GK + I ) transition via intermediate B , C states

Journal Article · Thu Aug 01 00:00:00 EDT 1991 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.461073· OSTI ID:5758787

Banerjee, S; Chakrabarti, M K; Bhattacharyya, S S; Saha, S ^[1]

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1. Atomic and Molecular Physics Section, Department of Materials Science, Indian Association for the Cultivation of Science, Calcutta-700 032, India (IN)

The generalized resonance enhanced two-photon dissociation (RETPD) cross sections of H{sub 2} are calculated for linear parallel polarizations of the two photon fields. The reduced density operator formalism is used to study the wavelength and quantum number dependences for the transitions {ital X} {sup 1}{Sigma}{sup +}{sub {ital g}} ({ital v}{sub {ital g}}=0, {ital J}{sub {ital g}}=0--4) {r arrow}{sup vuv} {ital B} {sup 1}{Sigma}{sup +}{sub {ital u}} ({ital C} {sup 1}{Pi}{sub {ital u}}) ({ital v}{sub {ital i}}=0,3, {ital J}{sub {ital i}}=0(1)--3) {r arrow}{sup uv}/visible (({ital EF}+{ital GK}){sup 1} {Sigma}{sup +}{sub {ital g}} +{ital I} {sup 1}{Pi}{sub {ital g}}, {ital E}{sub {ital f}}, {ital J}{sub {ital f}}). By resonant absorption of the first photon an aligned population in the intermediate {ital B}({ital C}) is created which is then dissociated by the second photon. The wavelength is so chosen that ionization from the resonant intermediate state is energetically forbidden. The contribution of the {ital EF} state to the total cross section is found to be negligible. The relative contribution of the {ital GK} and {ital I} states varies sharply with wavelength of the second photon and the resonant intermediate state. For both {ital B} and {ital C} states, dissociation through the {ital I} state is more prominent over a narrow range of wavelengths far from the dissociation threshold when the vibrational quantum number ({ital v}{sub {ital i}}) is large. For small {ital v}{sub {ital i}} the contribution of the {ital I} state is less. Due to the presence of a barrier above the dissociation threshold in the {ital I} state potential, narrow shape resonances occur. The cross sections at these shape resonances are a few orders of magnitude higher than the background.

• OSTI ID: 5758787
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 95:3; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
CHEMICAL REACTIONS
COLLISIONS
CROSS SECTIONS
DECOMPOSITION
DISSOCIATION
ELECTROMAGNETIC RADIATION
ELEMENTS
HYDROGEN
LASER RADIATION
MOLECULE COLLISIONS
MULTI-PHOTON PROCESSES
NONMETALS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PHOTON COLLISIONS
PHOTON-MOLECULE COLLISIONS
QUANTUM NUMBERS
RADIATIONS
RESONANCE ABSORPTION