Photolysis of 1-C4H9I and 2-C4H9I 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: Weinheim WILEY-VCH Verlag 23.03.2009; WILEY‐VCH Verlag; Wiley
• Subjects: alkyl iodides; Chemistry; Exact sciences and technology; General and physical chemistry; mass spectrometry; Photochemistry; photolysis; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); reaction mechanisms; velocity ion imaging; Branching; Structure effect; reaction mechanisms; Ions; alkyl iodides; Photodissociation; velocity ion imaging; Branched compound; Velocity; Photolysis; Imaging; Reaction mechanism; Iodocarbon; Mass spectrometry
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.200800742

Velocity ion imaging (see figure) is used to analyze the photodissociation mechanism of 1‐C4H9I (left image) and 2‐C4H9I (right image) at 266 nm. For 2‐C4H9I, 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. Photodissociation dynamics of 1‐C4H9I and 2‐C4H9I at 266 nm is investigated by velocity ion imaging. Photodissociation channels of 1‐C4H9I and 2‐C4H9I are analyzed and compared. For 1‐C4H9I the photodissociation dynamics only correlates with direct dissociation via repulsive surfaces. While for 2‐C4H9I, 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‐C4H9I than in that of 1‐C4H9I. Additionally, the curve‐crossing probability between 3Q0 and 1Q1 increases greatly with branching, from 0.31 for 1‐C4H9I to 0.70 for 2‐C4H9I in the prompt dissociation channel; the relative quantum yield for I* decreases strongly with branching, from 0.65 for 1‐C4H9I to 0.28 for 2‐C4H9I. Velocity ion imaging (see figure) is used to analyze the photodissociation mechanism of 1‐C4H9I (left image) and 2‐C4H9I (right image) at 266 nm. For 2‐C4H9I, 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.