Determination of spin-orbit branching fractions in the photodissociation of halogenated hydrocarbons

H. Fan, S. T. Pratt

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Two methods based on vacuum ultraviolet (vuv) photoionization are presented for the determination of the spin-orbit branching fractions of the halogen atom produced in the photodissociation of halogenated hydrocarbons. Both methods make use of differences in the photoionization cross sections of the 2P3/2 ground state and the 2P1/2 excited-state of the neutral halogen atom. In the first approach, measurements of the total photoionization signal of the halogen atom are made at several vuv wavelengths, and the difference in the wavelength dependences for the 2P3/2 and 2P1/2 atoms allows the extraction of the branching fractions. In the second approach, the vuv wavelength is set close to the ionization threshold of the 2P 3/2 atom (well above that of the 2P1/2 atom), and measurements are made at several electric field strengths, which shift the ionization threshold and thus vary the photoionization cross sections. In both methods, the relative cross sections of the ground- and excited-state atoms are determined by using the known branching fractions for the 266 nm photodissociation of methyl iodide. These methods are applied to the photodissociation of isopropyl iodide and allyl iodide, two systems for which standard ion-imaging techniques do not provide unique branching fractions.

Original languageEnglish
Pages (from-to)3901-3906
Number of pages6
JournalJournal of Physical Chemistry A
Volume111
Issue number19
DOIs
Publication statusPublished - May 17 2007
Externally publishedYes

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Halogenated Hydrocarbons
Photodissociation
photodissociation
Orbits
hydrocarbons
Photoionization
orbits
Atoms
Halogens
photoionization
atoms
halogens
iodides
Vacuum
Excited states
Wavelength
Ground state
vacuum
Ionization
cross sections

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Determination of spin-orbit branching fractions in the photodissociation of halogenated hydrocarbons. / Fan, H.; Pratt, S. T.

In: Journal of Physical Chemistry A, Vol. 111, No. 19, 17.05.2007, p. 3901-3906.

Research output: Contribution to journalArticle

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