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Article
Towards a Global Model of Spin-orbit Coupling in the Halocarbenes
Journal of Chemical Physics
  • Silver Nyambo
  • Cyrus Karshenas
  • Scott A. Reid
  • Phalgun Lolur
  • Richard Dawes, Missouri University of Science and Technology
Abstract
We report a global analysis of spin-orbit coupling in the mono-halocarbenes, CH(D)X, where X = Cl, Br, and I. These are model systems for examining carbene singlet-triplet energy gaps and spin-orbit coupling. Over the past decade, rich data sets collected using single vibronic level emission spectroscopy and stimulated emission pumping spectroscopy have yielded much information on the ground vibrational level structure and clearly demonstrated the presence of perturbations involving the low-lying triplet state. To model these interactions globally, we compare two approaches. First, we employ a diabatic treatment of the spin-orbit coupling, where the coupling matrix elements are written in terms of a purely electronic spin-orbit matrix element which is independent of nuclear coordinates, and an integral representing the overlap of the singlet and triplet vibrational wavefunctions. In this way, the structures, harmonic frequencies, and normal mode displacements from ab initio calculations were used to calculate the vibrational overlaps of the singlet and triplet state levels, including the full effects of Duschinsky mixing. These calculations have allowed many new assignments to be made, particularly for CHI, and provided spin-orbit coupling parameters and values for the singlet-triplet gaps. In a second approach, we have computed and fit full geometry dependent spin-orbit coupling surfaces and used them to compute matrix elements without the product form approximation. Those matrix elements were used in similar fits varying the anharmonic constants and singlet-triplet gap to reproduce the experimental levels. The derived spin-orbit parameters for carbenes CHX (X = Cl, Br, and I) show an excellent linear correlation with the atomic spin-orbit constant of the corresponding halogen, indicating that the spin-orbit coupling in the carbenes is consistently around 14% of the atomic value.
Department(s)
Chemistry
Research Center/Lab(s)
Center for High Performance Computing Research
Keywords and Phrases
  • Bromine,
  • Calculations,
  • Chlorine,
  • Computational geometry,
  • Iodine,
  • Organic compounds,
  • Ab initio calculations,
  • Coupling matrix element,
  • Single vibronic levels,
  • Singlet and triplet state,
  • Singlet-triplet energy gap,
  • Spin-orbit parameters,
  • Stimulated emission pumping,
  • Vibrational level structures,
  • Matrix algebra
Document Type
Article - Journal
Document Version
Final Version
File Type
text
Language(s)
English
Rights
© 2015 American Institute of Physics (AIP), All rights reserved.
Publication Date
6-1-2015
Citation Information
Silver Nyambo, Cyrus Karshenas, Scott A. Reid, Phalgun Lolur, et al.. "Towards a Global Model of Spin-orbit Coupling in the Halocarbenes" Journal of Chemical Physics Vol. 142 Iss. 21 (2015) ISSN: 0021-9606
Available at: http://works.bepress.com/richard_dawes/37/