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

• Published in: Chemphyschem Vol. 10; no. 5; pp. 830 - 834
• Main Authors: Liu, Yuzhu, Zheng, Qiusha, Zhang, Yan, Zhang, Rongrong, Wang, Yanmei, Zhang, Bing
• Format: Journal Article
• Language: English
• Published: 23.03.2009
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.200800742

Abstract 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 CI stretch, coupled with some bending motions. magnified image 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 CI 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.