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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ionic Pathways following UV Photoexcitation of the (HI)2 van der Waals Dimer
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Ionic Pathways following UV Photoexcitation of the (HI)2 van der Waals Dimer

机译：（HI）2 van der Waals Dimer的UV光激发后的离子途径

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摘要

Photodissociation of the (HI)2 van der Waals dimers at 248 nm and nearby wavelengths has been studied using time-of-flight mass spectrometry and velocity map imaging. I2 + product ions with a translational temperature of 130 K and “translationally hot” I+ ions with an average kinetic energy of Et ) 1.24 ( 0.03 eV and angular anisotropy ) 1.92 ( 0.11 were detected as dimer-specific ionic photofragments. Velocity map images of the I2 + and I+ species were found to be qualitatively similar to those observed in the case of photoexcitation of the (CH3I)2 dimer (J. Chem. Phys. 2005, 122, 204301). As in the case of the (CH3I)2 dimer, the absence of neutral I2-specific features in the ionic species images from (HI)2 allows us to eliminate neutral molecular I2 as a precursor of I+ and I2 +. Similar to the case of (CH3I)2, we deduce that the observed I2 + ions are produced in their 2Π3/2,g ground electronic state as a result of photodissociation of the ionized dimer (HI)2 + + h f I2 + + .... The formation of “translationally hot” I+ ions is attributed to photodissociation of nascent vibrationally excited I2 + with an average vibrational energy of 1.05 ( 0.10 eV. This vibrational excitation is explained by the nonequilibrium initial I-I distance in I2 + arising in photodissociation of (HI)2 + after prompt release of the light H atoms. On the basis of our ab initio calculated value for the I-I distance of (3.17 ) in the (HI)2 + precursor dimer, the vibrational excitation of I2 + is expected to be 1.02 eV, which is in quantitative agreement with our experimentally deduced value. The interpretation of our results was supported by ab initio calculations of the structure and energy of neutral and ionized dimers of HI at the MP4(SDTQ)//MP2 level.
机译：（HI）2范德华二聚体在248 nm和附近波长的光解离已使用飞行时间质谱和速度图成像技术进行了研究。平移温度为130 K的I2 +产物离子和平均动能为Et的“平移热” I +离子1.24（0.03 eV和角各向异性）1.92（0.11）被检测为二聚体特异性离子型光电子碎片。发现I2 +和I +物种在质量上与（CH3I）2二聚体光激发时观察到的相似（J. Chem。Phys。2005，122，204301）。 （2）二聚体，（HI）2的离子种类图像中不存在中性的I2-特定特征，这使我们能够消除作为I +和I2 +的前体的中性分子I2。与（CH3I）2的情况类似，我们推断由于电离的二聚体（HI）2 + + hf I2 + + ... ...的光解作用，观察到的I2 +离子以其2Π3/ 2，g基态电子态产生。归因于新生振动激发的I2 +的光解离，其平均振动能为1.05（0.10 eV。这种振动激发由迅速释放轻的H原子后（HI）2 +的光解离引起的I2 +中的非平衡初始I-I距离解释。根据我们从头算出的（HI）2 +前体二聚体中II距离（3.17）的计算值，I2 +的振动激发预计为1.02 eV，这与我们的实验推论值在数量上相符。从头开始计算HI的中性和离子化二聚体在MP4（SDTQ）// MP2水平上的结构和能量，可以支持我们对结果的解释。

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