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Theory of resonantly enhanced multiphoton processes in molecules

Dixit, S. N. and McKoy, V. (1985) Theory of resonantly enhanced multiphoton processes in molecules. Journal of Chemical Physics, 82 (8). pp. 3546-3553. ISSN 0021-9606.

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In this paper we formulate a theory for the analysis of resonant enhanced multiphoton ionization processes in molecules. Our approach consists of viewing the (n+m) photon ionization process from an isotropic initial state as m‐photon ionization out of an oriented, excited state. The orientation in this resonant state, which is reached by n‐photon excitation from the initial state, is nonisotropic, and is characteristic of this absorption process. The ionization simply probes this anisotropic population. The calculation of the REMPI process thus consists of determining the anisotropy created in the resonant state and then coupling this anisotropic population to ionization out of it. While the former is accomplished by the solution of appropriate density matrix equations, the latter is done by coupling these density matrix elements to angle‐resolved ionization rates out of this state. An attractive feature of this approach is that the influence of saturation effects, and other interactions, such as collisions, on the photoelectron properties is easily understood and incorporated. General expressions are derived for photoelectron angular distributions. Based on these, several properties of the angular distributions that follow purely on symmetry considerations are discussed. One of the new features that emerge out of this work is the saturation induced anisotropy in REMPI. In this effect higher order contributions to the angular distributions appear since saturation influences different ionization channels differently thereby creating an additional anisotropy in the excited state.

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Additional Information:© 1985 American Institute of Physics. Received 16 August 1984; accepted 5 October 1984. One of us (S.N.D.) acknowledges useful discussions with Peter Lambropoulos. This material is based upon research supported by the National Science Foundation under Grant No. CHE-8218166.
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Issue or Number:8
Classification Code:PACS: 33.80.Rv
Record Number:CaltechAUTHORS:20120628-111541172
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Official Citation: Theory of resonantly enhanced multiphoton processes in molecules S. N. Dixit and V. McKoy J. Chem. Phys. 82, 3546 (1985);
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32171
Deposited By: Ruth Sustaita
Deposited On:28 Jun 2012 18:26
Last Modified:03 Oct 2019 03:58

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