Production of I∗(2P½) in the ultraviolet photodissociation of α-branched alkyl iodides

Uma, S. ; Das, Puspendu Kumar (1996) Production of I∗(2P½) in the ultraviolet photodissociation of α-branched alkyl iodides Journal of Chemical Physics, 104 (12). pp. 4470-4474. ISSN 0021-9606

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Photodissociation dynamics of a series of α-branched alkyl iodides at excitation wavelengths of 222, 266, and ~305 nm has been investigated by measuring the quantum yield (ϕ∗) of I∗(2P½) production. I is found to be the major product at 222 nm and 266 nm from methyl and ethyl iodides but not from the higher α-branched homologs. On the contrary, I(2P3/2) is the major product at ~305 nm for all the iodides. Assuming that I∗ originates from the 3Q0 state over the entire A-band, production of both I and I* in methyl and ethyl iodides at 222 and 266 nm is explained by invoking the curve-crossing mechanism in the upper state. The crossing probability (P) between the 3Q0 and 1Q1 surfaces for these two molecules has been estimated. At ~305 nm, simultaneous excitation to the 3Q0 and 3Q1 states remains a distinct possibility. For higher branched (i.e., i-propyl and t-butyl) alkyl iodides, the mechanism for I∗production is qualitatively different from that of unbranched iodides. Coupling of α-carbon bending vibrational modes with the C-I bond excitation as well as the actual time spent in the excited state surfaces in i-propyl and t-butyl iodides seem to be the reasons for altering the dynamics of dissociation drastically in comparison with that of methyl iodide.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
Keywords:Alkyl Compounds; Photodissociation; Fragmentation; Iodides; Ultraviolet Radiation; Vibrational States
ID Code:86337
Deposited On:09 Mar 2012 10:39
Last Modified:09 Mar 2012 10:39

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