"Theoretical and electron spin resonance studies of the the H···‹ H, H·" by Lon B. Knight, William E. Rice et al.
 

Theoretical and electron spin resonance studies of the the H···‹…H, H···D, and D···‹…D spin-pair radicals in rare gas matrices: A case of extreme singlet-triplet mixing

ACS Citation

Knight, L. B.; Rice, W. E.; Moore, L.; Davidson, E. R.; Dailey, R. S. Theoretical and electron spin resonance studies of the the H···‹…H, H···D, and D···‹…D spin-pair radicals in rare gas matrices: A case of extreme singlet-triplet mixing. J. Chem. Phys. 1998, 109, 1409-1409.

Abstract

The H···‹…H, H···D, and D···‹…D spin-pair radicals have been thoroughly investigated in neon, argon, krypton, and xenon matrices near 4 K by electron spin resonance (ESR). A theoretical model has been developed that treats these spin-pairs as weakly interacting atoms. The model includes the effects of 3Σ/1Σ mixing in the analysis of the observed ESR spectral results and yields a consistent set of magnetic parameters for these three isotopomers in all four rare gas hosts. The consideration of H atoms interacting with other H atoms over a distribution of internuclear distances in the rare gas lattice is included in the theoretical and experimental analyses. Application of the model to earlier ESR results for H···CH3 reveals a value for its Heisenberg exchange interaction (J) which is found to be considerably larger than that for the H···H spin-pair. The effects of methane and neon on the J value are calculated for these spin-pairs. The H···H case is unusual in that the nuclear hyperfineinteraction (A) is considerably larger than D (the anisotropic dipole-“dipole magnetic interaction between electrons) which is much larger than J. The H···H spin-pairs exhibit internuclear distances greater than 7 Å and have the following magnetic parameters (MHz) based upon this model of -œweakly interacting atoms;- giso =2.0016, Aiso =1426, D=-200, and J=6. Since a distribution of distances is involved, other spin-pairs would be separated by even greater distances in the matrix and thus have smaller absolute values of D and J.

Source Name

Journal of Chemical Physics

Publication Date

1-1-1998

Volume

109

Issue

4

Page(s)

2732-2738

Document Type

Citation

Citation Type

Article

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