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Possible role for triplet H/sub 2/CN/sup +/ isomers in the formation of HCN and HNC in interstellar clouds

Journal Article · · J. Chem. Phys.; (United States)
OSTI ID:5051799
The structures and energies of the lowest triplet states of four isomers of H/sub 2/CN/sup +/ have been determined by self-consistent field and configuration interaction calculations. When both hydrogen atoms are attached to the nitrogen atom, H/sub 2/NC/sup +/, the molecule has its lowest triplet state energy, which is 97.2 kcal mol/sup -1/ above the energy of the linear singlet ground state. The structure has C/sub 2v/ symmetry, with an HCH bond angle of 116.8/sup 0/, and bond lengths of 1.009 A (H--N) and 1.268 A (N--C). Other isomers investigated include the H/sub 2/CN/sup +/ isomer at 104.7, the cis-HCNH/sup +/ isomer at 105.3, and the trans-HCNH/sup +/ isomer at 113.6 kcal mol/sup -1/. The H/sub 2/CN/sup +/ isomer has an unusual ''carbonium nitrene'' structure, with a C--N bond length of 1.398 A. It is suggested that the triplet H/sub 2/NC/sup +/ isomer may play a role in determining the relative yields of HCN and HNC from the reaction of C/sup +/ and NH/sub 3/. Specifically, a triplet path is postulated in which C/sup +/ and NH/sub 3/ yield the triplet H/sub 2/NC/sup +/ isomer, which then yields the singlet H/sub 2/NC/sup +/ isomer by phosphorescent emission. Because this emission removes a large amount of energy, the singlet H/sub 2/NC/sup +/ isomer may have insufficient energy to isomerize to the linear singlet ground state. Subsequent dissociative recombination would yield the HNC isomer exclusively.
Research Organization:
Department of Chemistry, University of California, Davis, California 95616
OSTI ID:
5051799
Journal Information:
J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 73:7; ISSN JCPSA
Country of Publication:
United States
Language:
English