Li Guosheng, Hwang Hyun Jin
Department of Chemistry, Kyung Hee University, Seoul 130-701, South Korea.
J Chem Phys. 2006 Jun 28;124(24):244306. doi: 10.1063/1.2212938.
High-resolution photofragment translational spectroscopy is used in this work to measure the translational and internal energy distributions in the CD3 and iodine fragments produced from the photodissociation of CD3I at 266 and 304 nm. Channel selected detection, via resonantly enhanced multiphoton ionization, combined with one-dimensional core sampling provides detailed information about vibrational state distributions of the CD3 fragments. The vibrational state distributions of CD3 fragments in the I*(2P12) channel have a propensity of nu2 ' umbrella bending mode with a maximum at nu2 ' = 1 for 266 nm photodissociation. For I*(2P12) channel at 304 nm photodissociation, vibrational state distributions of CD3 fragment have a maximum in the vibrational ground state. For the I(2P32) channel (1Q1 <-- 3Q(0+)), nu2 ' umbrella bending vibrational distribution is measured as the predominant vibrational mode but has a much broader distribution when compared to that of the I* channel. The vibrational state distributions of the CD3 fragment produced from the perpendicular transition, i.e., 3Q1, which was determined at 304 nm photodissociation, has a maximum at nu2 ' = 1. The curve crossing possibility between the 1Q1 and 3Q(0+) adiabatic potentials is determined as 0.19 for 266 and 0.85 for 304 nm. The trend in reaction dynamics in 266 and 304 nm photodissociation of CD3I is compared with theoretical calculations. A bond dissociation energy D0(C-I) = 56.60+/-0.5 kcal/mol was derived by applying laws of energy conservation.
在本工作中，采用高分辨率光碎片平移光谱法来测量在266和304 nm波长下CD3I光解离产生的CD3和碘碎片的平移和内能分布。通过共振增强多光子电离进行通道选择检测，并结合一维核心采样，可提供有关CD3碎片振动状态分布的详细信息。在I*(2P12)通道中，对于266 nm光解离，CD3碎片的振动状态分布倾向于ν2'伞形弯曲模式，在ν2' = 1时达到最大值。对于304 nm光解离的I*(2P12)通道，CD3碎片的振动状态分布在振动基态达到最大值。对于I(2P32)通道（1Q1 <-- 3Q(0+)），测量到ν2'伞形弯曲振动分布是主要的振动模式，但与I*通道相比，其分布要宽得多。在304 nm光解离时确定的由垂直跃迁即3Q1产生的CD3碎片的振动状态分布在ν2' = 1时达到最大值。对于266 nm，1Q1和3Q(0+)绝热势之间的曲线交叉可能性确定为0.19，对于304 nm为0.85。将CD3I在266和304 nm光解离中的反应动力学趋势与理论计算进行了比较。通过应用能量守恒定律得出键解离能D0(C-I) = 56.60±0.5 kcal/mol。
