Martin Marion R, Brown Davida J Ankeny, Chiou Albert S, Zare Richard N
Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.
J Chem Phys. 2007 Jan 28;126(4):044315. doi: 10.1063/1.2431368.
The effects of vibrational excitation on the Cl+CD(4) reaction are investigated by preparing three nearly isoenergetic vibrational states: mid R:3000 at 6279.66 cm(-1), |2100> at 6534.20 cm(-1), and |1110> at 6764.24 cm(-1), where |D(1)D(2)D(3)D(4)> identifies the number of vibrational quanta in each C-D oscillator. Vibrational excitation of the perdeuteromethane is via direct infrared pumping. The reaction is initiated by photolysis of molecular chlorine at 355 nm. The nascent methyl radical product distribution is measured by 2+1 resonance-enhanced multiphoton ionization at 330 nm. The resulting CD(3) state distributions reveal a preference to remove all energy available in the most excited C-D oscillator. Although the energetics are nearly identical, the authors observe strong mode specificity in which the CD(3) state distributions markedly differ between the three Cl-atom reactions. Reaction with CD(4) prepared in the |3000> mode leads to CD(3) products populated primarily in the ground state, reaction with CD(4) prepared in the |2100> mode leads primarily to CD(3) with one quantum of stretch excitation, and reaction with CD(4) prepared in the |1110> mode leads primarily to CD(3) with one quantum of C-D stretch excitation in two oscillators. There are some minor deviations from this behavior, most notably that the Cl atom is able to abstract more energy than is available in a single C-D oscillator, as in the case of |2100>, wherein a small population of ground-state CD(3) is observed. These exceptions likely result from the mixings between different second overtone stretch combination bands. They also measure isotropic and anisotropic time-of-flight profiles of CD(3) (nu(1)=1,2) products from the Cl+CD(4) |2100> reaction, providing speed distributions, spatial anisotropies, and differential cross sections that indicate that energy introduced as vibrational energy into the system essentially remains as such throughout the course of the reaction.
通过制备三个近等能量的振动状态来研究振动激发对Cl + CD₄反应的影响：在6279.66 cm⁻¹处的中R：3000、在6534.20 cm⁻¹处的|2100>以及在6764.24 cm⁻¹处的|1110>，其中|D₁D₂D₃D₄>表示每个C - D振子中的振动量子数。全氘代甲烷的振动激发是通过直接红外泵浦实现的。反应由355 nm处分子氯的光解引发。新生甲基自由基产物分布通过330 nm处的2 + 1共振增强多光子电离进行测量。所得的CD₃态分布显示出优先去除最激发的C - D振子中所有可用能量的倾向。尽管能量几乎相同，但作者观察到强烈的模式特异性，其中在三个Cl原子反应之间，CD₃态分布明显不同。与处于|3000>模式制备的CD₄反应导致主要处于基态的CD₃产物，与处于|2100>模式制备的CD₄反应主要导致具有一个拉伸激发量子的CD₃，与处于|1110>模式制备的CD₄反应主要导致在两个振子中具有一个C - D拉伸激发量子的CD₃。存在一些与这种行为的轻微偏差，最显著的是Cl原子能够提取比单个C - D振子中可用能量更多的能量，例如在|2100>的情况下，其中观察到少量基态CD₃。这些例外可能是由于不同的二次泛音拉伸组合带之间的混合导致的。他们还测量了来自Cl + CD₄ |2100>反应的CD₃（ν₁ = 1,2）产物的各向同性和各向异性飞行时间分布，提供了速度分布、空间各向异性和微分截面，表明作为振动能量引入系统的能量在反应过程中基本上保持不变。
