Roaming signature in photodissociation of carbonyl compounds

IF 2.5 2区 化学 Q3 CHEMISTRY, PHYSICAL
K. Lin, Po-Yu Tsai, Meng-Hsuan Chao, M. Nakamura, T. Kasai, A. Lombardi, F. Palazzetti, V. Aquilanti
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引用次数: 7

Abstract

ABSTRACT An alternative to the transition state (TS) pathway, the roaming route, which bypasses the minimum energy path but produces the same molecular products, was recently found in photodissociation dynamics. This account describes signatures of roaming in photodissociation of the carbonyl compounds, specifically methyl formate and aliphatic aldehydes. Methyl formate was promoted to the excited state, followed by internal conversion via a conical intersection. Then, the energetic precursor dissociated to fragments which proceeded along either TS or roaming path. In contrast to the lack of a roaming saddle point found in methyl formate, the structure of the roaming saddle point for each of a series of aliphatic aldehydes comprises two moieties that are weakly bound at a distance. As its size increases, the energy difference between the TS barrier and the roaming saddle point increases and the roaming pathway becomes increasingly dominant. Experimentally, the rotational-level dependence of the roaming route was measured with ion imaging, while the vibrational-state dependence was observed with time-resolved Fourier-transform infrared emission spectroscopy. The roaming signature was verified theoretically by quasi-classical trajectory (QCT) calculations. As an alternative to the QCT method, a multi-center impulsive model was developed to simulate the roaming scalar and vector properties.
羰基化合物光解过程中的漫游特征
最近在光解动力学中发现了一种替代过渡态(TS)途径的漫游途径,它可以绕过最小能量路径,但产生相同的分子产物。这个帐户描述漫游的签名在羰基化合物的光解,特别是甲酸甲酯和脂肪族醛。甲酸甲酯被提升到激发态,然后通过一个锥形交叉进行内部转化。然后,能量前体分解成沿着TS或漫游路径前进的碎片。与甲酸甲酯中缺乏漫游鞍点相反,一系列脂肪族醛的漫游鞍点结构由两个在一定距离上弱结合的基团组成。随着其大小的增大,TS势垒与漫游鞍点之间的能量差增大,漫游路径日益占主导地位。实验上,利用离子成像测量漫游路径的旋转水平依赖性,用时间分辨傅里叶变换红外发射光谱观察漫游路径的振动状态依赖性。通过准经典轨迹(QCT)计算从理论上验证了漫游特征。作为QCT方法的替代方案,提出了一种多中心脉冲模型来模拟漫游标量和矢量特性。
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来源期刊
CiteScore
14.20
自引率
1.60%
发文量
5
审稿时长
1 months
期刊介绍: International Reviews in Physical Chemistry publishes review articles describing frontier research areas in physical chemistry. Internationally renowned scientists describe their own research in the wider context of the field. The articles are of interest not only to specialists but also to those wishing to read general and authoritative accounts of recent developments in physical chemistry, chemical physics and theoretical chemistry. The journal appeals to research workers, lecturers and research students alike.
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