Comparison of the cis-bending and C-H stretching vibration on the reaction of C2H2+ with H2 using laser induced reactions.
Comparison of the cis-bending and C-H stretching vibration on the reaction of C2H2+ with H2 using laser induced reactions.
复制标题
使用激光诱导反应比较 C2H2 与 H2 反应的顺式弯曲和 C-H 伸缩振动。
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
T. Giesen
中科院分区：
文献类型：
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作者：
S. Schlemmer;O. Asvany;T. Giesen
利用自由电子激光FELIX的宽可调性，利用22极离子阱中C2H2(+) + H2的激光诱导反应（LIR）检测了乙炔母离子的v3 C-H伸缩振动和v5顺式弯曲振动。确定弯曲振动的振动频率omega5和相应的Renner-Teller参数epsilon5分别为710 cm（-1）和0.03。这些结果与以前的实验工作有很大的不同，但与最近和最先进的理论工作一致。系统地研究了两种振动模式的lir信号与激光功率、存储时间和氢碰撞伙伴数密度的关系。建立了描述LIR过程中所有步骤的反应方案。对相应的速率方程组进行了数值求解。在假定激发母离子以等于朗之万极限的净速率系数松弛或反应的情况下，由该解确定了振动激发态tau3 = (3 +/- 1) ms和t5 = (200 +/- 50) ms的寿命和振动偶极矩micro3 = 0.19(2) D和micro2 = 0.21(2) D。C-H拉伸振动的寿命与先前的LIR实验和从头计算一致。碳氢键拉伸在促进氢的提取方面比弯曲要高效一个数量级。基于吸氢的能量学和C2H2+入口通道中复合物形成的可能抑制，讨论了这种强模式依赖性。H2碰撞系统。
Laser induced reaction (LIR) of C2H2(+) + H2 in a 22-pole ion trap at 90 K has been employed to detect the v3 C-H stretching vibration and the v5 cis bending vibration of the acetylene parent ion using the wide tunability of the free electron laser FELIX. The vibrational frequency of the bending vibration, omega5, and the corresponding Renner-Teller parameter, epsilon5, are determined to be 710 cm(-1) and 0.03, respectively. These results differ quite substantially from previous experimental work but are in line with the most recent and advanced theoretical work. The dependence of the LIR-signal of the two vibrational modes is studied systematically with respect to the laser power, storage time, and number density of the hydrogen collision partner. A reaction scheme describing all steps involved in the LIR process is set up. The corresponding rate equation system is solved numerically. From this solution the lifetimes for the vibrational excited states, tau3 = (3 +/- 1) ms and t5 = (200 +/- 50) ms and the vibrational dipole moments micro3 = 0.19(2) D and micro2 = 0.21(2) D are determined under the assumption that the excited parent ion relaxes or reacts with a net rate coefficient equal to the Langevin limit. The lifetime for the C-H stretching vibration is in agreement with a previous LIR experiment and with ab initio calculations. C-H stretching turns out to be about an order of magnitude more efficient than bending in promoting hydrogen abstraction. This strong mode dependence is discussed on the basis of the energetics for hydrogen abstraction and a possible inhibition of complex formation in the entrance channel of the C2H2+..H2 collision system.