Vinylidene: Potential energy surface and unimolecular reaction dynamics
New quantum chemistry calculations (with a triple zeta plus polarization basis set, and a single and double configuration interaction) have been carried out to determine the equilibrium points and the transition state for the vinylidene (H/sub 2/C = C:)..-->..acetylene (HCequivalentCH) isomerization. A classical barrier height (i.e., with no zero point energy effects) of 6.3 kcal/mol is obtained, and application of the Davidson correction for unlinked clusters reduces this to 5.4 kcal/mol. Our best estimate is that the true classical barrier lies in the range 2--4 kcal/mol. The dynamics of the vinylidene/acetylene isomerization is described with the framework of the reaction path Hamiltonian. The lifetime of vinylidene (in its ground vibrational state) with respect to this process is calculated to be 0.24 to 4.6 ps for a classical barrier of 2 to 4 kcal/mol. This lifetime decreases by a factor of approx.2 if one quantum of the CH/sub 2/ scissors mode of vinylidene is excited, but is predicted to increase somewhat if a quantum of the C--C stretch is excited. These results are all consistent with the recent experimental observation of vinylidene via photodetachment of C/sub 2/H/sup -//sub 2/.
- Research Organization:
- Department of Chemistry and Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
- OSTI ID:
- 6572126
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 80:9; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Vinylidene: a very shallow minimum on the C2H2 potential energy surface
Vinylidene radical cation: A sizable barrier to unimolecular rearrangement to the acetylene radical cation