A comparative classical-quantum study of the photodissociation of water in the B̃ band

Rob Van Harrevelt, Marc C. Van Hemert, George C Schatz

Research output: Contribution to journalArticle

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Abstract

A detailed comparison between three-dimensional classical surface hopping calculations and quantum mechanical calculations is presented for the photodissociation of water in the B band. Accurate coupled diabatic potential energy surfaces are used in these calculations. Tully's "fewest switches" method using an adiabatic representation for the electronic states is applied for the surface hopping procedure. Studied are the energy dependence of the branching ratios for the possible fragmentation channels, including electronically nonadiabatic channels, and the probabilities for particular vibrational or rotational product states of the electronically excited OH(A) fragment. Although the classical results generally agree well with the quantum results, some serious errors in the classical calculations were detected. First, it is found that the calculated fractions for the O(1D) + H2 and O(3P) + H + H fragments are too large. Second, the absence of quantization of the vibrational energy in classical mechanics has consequences for the details of the rotational product state distribution of the OH(A,ν=0) fragments. This is important for the "single N phenomenon", an experimentally observed strong preference for populating the highest rotational product state for which the rotational barrier energy is lower than the available energy (S.A. Harich, X.F. Yang, R. van Harrevelt, and M.C. van Hemert, Phys. Rev. Lett., 2001). For a two-dimensional model, where the above-mentioned problems of classical trajectory calculations do not occur, excellent agreement between classical and quantum results is found. Classical trajectories were followed to explain the single N phenomenon and the origin of the experimentally observed vibrational excitation of OH(A) fragments.

Original languageEnglish
Pages (from-to)11480-11487
Number of pages8
JournalJournal of Physical Chemistry A
Volume105
Issue number51
DOIs
Publication statusPublished - Dec 27 2001

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Photodissociation
photodissociation
fragments
Water
water
products
Trajectories
trajectories
Potential energy surfaces
energy
classical mechanics
Energy barriers
Electronic states
two dimensional models
Mechanics
fragmentation
switches
potential energy
Switches
electronics

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

A comparative classical-quantum study of the photodissociation of water in the B̃ band. / Van Harrevelt, Rob; Van Hemert, Marc C.; Schatz, George C.

In: Journal of Physical Chemistry A, Vol. 105, No. 51, 27.12.2001, p. 11480-11487.

Research output: Contribution to journalArticle

Van Harrevelt, Rob ; Van Hemert, Marc C. ; Schatz, George C. / A comparative classical-quantum study of the photodissociation of water in the B̃ band. In: Journal of Physical Chemistry A. 2001 ; Vol. 105, No. 51. pp. 11480-11487.
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