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Photolysis of 1‐C 4 H 9 I and 2‐C 4 H 9 I at 266 nm: Direct Observation of the Effect of Branching on the Photodissociation Mechanism
Author(s) -
Liu Yuzhu,
Zheng Qiusha,
Zhang Yan,
Zhang Rongrong,
Wang Yanmei,
Zhang Bing
Publication year - 2009
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200800742
Subject(s) - photodissociation , dissociation (chemistry) , chemistry , quantum yield , ion , branching fraction , analytical chemistry (journal) , atomic physics , crystallography , photochemistry , fluorescence , physics , optics , organic chemistry , chromatography
Velocity ion imaging (see figure) is used to analyze the photodissociation mechanism of 1‐C 4 H 9 I (left image) and 2‐C 4 H 9 I (right image) at 266 nm. For 2‐C 4 H 9 I, a new channel for formation of I and I* atoms is observed. It is attributed to the repulsive mode along the CI stretch, coupled with some bending motions.Photodissociation dynamics of 1‐C 4 H 9 I and 2‐C 4 H 9 I at 266 nm is investigated by velocity ion imaging. Photodissociation channels of 1‐C 4 H 9 I and 2‐C 4 H 9 I are analyzed and compared. For 1‐C 4 H 9 I the photodissociation dynamics only correlates with direct dissociation via repulsive surfaces. While for 2‐C 4 H 9 I, a new formation channel of I and I* atoms is observed. It is attributed to the repulsive mode along the CI stretch, coupled with some bending motions. As the alkyl group becomes more branched, the contribution of bending modes to I and I* is much more obvious in the photodissociation of 2‐C 4 H 9 I than in that of 1‐C 4 H 9 I. Additionally, the curve‐crossing probability between 3 Q 0 and 1 Q 1 increases greatly with branching, from 0.31 for 1‐C 4 H 9 I to 0.70 for 2‐C 4 H 9 I in the prompt dissociation channel; the relative quantum yield for I* decreases strongly with branching, from 0.65 for 1‐C 4 H 9 I to 0.28 for 2‐C 4 H 9 I.