Ion-pair formation mechanisms in chloromethane, bromomethane and dichlorodifluoromethane

D. A. Shaw, D. M P Holland, I. C. Walker

Research output: Contribution to journalArticle

Abstract

The first absolute photoion-pair cross sections have been derived from measurements of the absolute photoabsorption cross section and the photoion-pair quantum efficiency. The results for CH3Cl, CH3Br and CF2Cl2 show that direct transitions into ion-pair states play a significant role. In each molecule, the structure in the photoion-pair spectrum is different to that in the photoabsorption spectrum and often does not resemble the strong bands, due to Rydberg transitions, prominent in the latter spectra. At photon energies associated with excitations into Rydberg states, and consequently with peaks in absorption, the photoion-pair quantum efficiency usually exhibits a local minimum. This indicates that the Rydberg state decays preferentially by predissociation into a state yielding neutral fragments rather than by predissociation into a state evolving into ion pairs. © 2006 IOP Publishing Ltd.

Original languageEnglish
Article number012
Pages (from-to)3549-3560
Number of pages12
JournalJournal of Physics B: Atomic, Molecular and Optical Physics
Volume39
Issue number17
DOIs
Publication statusPublished - 14 Sep 2006

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photoabsorption
quantum efficiency
ions
cross sections
fragments
photons
decay
excitation
molecules
energy

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Ion-pair formation mechanisms in chloromethane, bromomethane and dichlorodifluoromethane. / Shaw, D. A.; Holland, D. M P; Walker, I. C.

In: Journal of Physics B: Atomic, Molecular and Optical Physics, Vol. 39, No. 17, 012, 14.09.2006, p. 3549-3560.

Research output: Contribution to journalArticle

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T1 - Ion-pair formation mechanisms in chloromethane, bromomethane and dichlorodifluoromethane

AU - Shaw, D. A.

AU - Holland, D. M P

AU - Walker, I. C.

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AB - The first absolute photoion-pair cross sections have been derived from measurements of the absolute photoabsorption cross section and the photoion-pair quantum efficiency. The results for CH3Cl, CH3Br and CF2Cl2 show that direct transitions into ion-pair states play a significant role. In each molecule, the structure in the photoion-pair spectrum is different to that in the photoabsorption spectrum and often does not resemble the strong bands, due to Rydberg transitions, prominent in the latter spectra. At photon energies associated with excitations into Rydberg states, and consequently with peaks in absorption, the photoion-pair quantum efficiency usually exhibits a local minimum. This indicates that the Rydberg state decays preferentially by predissociation into a state yielding neutral fragments rather than by predissociation into a state evolving into ion pairs. © 2006 IOP Publishing Ltd.

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