Electronic Population Inversion in HCCO/DCCO Products from Hyperthermal Collisions of O((3)P) with HCCH/DCCD.
The dynamics of hyperthermal O((3)P) reactions with acetylene have been investigated with the use of crossed molecular beams techniques, employing both mass spectrometric and optical detection of products. With collision energies of 40-150 kcal mol(-1), O((3)P) + HCCH/DCCD → HCCO/DCCO + H/D may follow multiple pathways to form the ketenyl radical (HCCO or DCCO) in ground doublet states or in electronically excited quartet and doublet states. Theoretical calculations support the assignment of the various reaction pathways. The fraction of electronic excitation is substantial. At the highest collision energy studied, ∼65% of the ketenyl radical products that survive are electronically excited, with the majority of the excited products in a quartet state. In this case, a population inversion exists between the electronically excited quartet and ground doublet states of the ketenyl product. Such significant electronic excitation in products is unusual in bimolecular reactions, especially when ground-state products are accessible by spin-allowed pathways.
§Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
Sridhar A
SA
Lahankar
§Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
Jianming
J
Zhang
‡Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States.
Sophya
S
Garashchuk
∥Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States.
George C
GC
Schatz
§Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.|⊥Visiting Research Fellow at the Dalian Institute of Chemical Physics, State Key Laboratory of Molecular Reaction Dynamics, 457 Zhongshan Road, Dalian 116023, Liaoning, People's Republic of China.
Timothy K
TK
Minton
acetylene; hyperthermal atomic oxygen; ketenyl radical; population inversion