Electronic state-selective photodissociation of CH/sub 2/BrI at 248, 210, and 193 nm

Journal Article · Sun Feb 15 00:00:00 EST 1987 · J. Chem. Phys.; (United States)

OSTI ID:6925739

Butler, L J; Hintsa, E J; Shane, S F; Lee, Y T

The primary photodissociation channels of CH/sub 2/BrI following excitation at 193.3, 210, and 248.5 nm have been studied with the crossed laser-molecular beam technique. Product translational energy distributions and polarization dependences were derived for the primary dissociation processes observed. The data demonstrate bond selective photochemistry as well as some selective formation of electronically excited photofragments in bond fission and concerted dissociation. Excitation at 248.5 nm, which is assigned to excitation of primarily a n(I)..-->..sigma*(C--I) transition with some contribution from an overlapping n(Br)..-->..sigma*(C--Br) transition, results in both C--I and C--Br bond fission. C--I bond fission is the dominant channel, producing I atoms in both the /sup 2/P/sub 3/2/ and spin-orbit excited /sup 2/P/sub 1/2/ states in a ratio of 1.0:0.75. Excitation at 193.3 nm, assigned to a transition to primarily predissociated Rydberg levels on the I atom, leads to C--Br bond fission, some C--I bond fission, and significant concerted elimination of IBr. Analysis of the product translational energy distributions for the dissociation products indicates that the IBr is formed electronically excited and that the halogen atom products are spin-orbit excited. Excitation at 210 nm, of the transition assigned as n(Br)..-->..sigma*(C--Br) based on comparison with CH/sub 3/Br, results in selective breaking of the stronger C--X bond in the molecule, the C--Br bond, and no fission of the C--I bond. Some concerted elimination of IBr also occurs; the IBr velocity distribution indicates it is probably formed electronically excited as in photolysis at 193.3 nm.

• Research Organization: Materials and Molecular Research Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720
• OSTI ID: 6925739
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 86:4; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640301* -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BEAMS
BROMINATED ALIPHATIC HYDROCARBONS
CHEMICAL BONDS
CHEMICAL REACTIONS
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ELECTRONIC STRUCTURE
ENERGY LEVELS
EXCITED STATES
HALOGENATED ALIPHATIC HYDROCARBONS
IODINATED ALIPHATIC HYDROCARBONS
LASER RADIATION
MOLECULAR BEAMS
ORGANIC BROMINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADIATIONS
RYDBERG STATES
SPECTRA
ULTRAVIOLET SPECTRA