Ray Sara E, McCoy Anne B, Glennon John J, Darr Joshua P, Fesser Elizabeth J, Lancaster Jeffrey R, Loomis Richard A
Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
J Chem Phys. 2006 Oct 28;125(16):164314. doi: 10.1063/1.2363378.
The laser-induced fluorescence and action spectra of I2 in a helium supersonic expansion have been recorded in the I2 B-X, 20-0 region. Two features are identified within the spectra. The lower-energy feature arises from transitions between states that are localized in a T-shaped conformation on both the X- and B-state potentials. The higher-energy feature reflects transitions from states that are localized in a linear conformation on the X state to states that have energies that are larger than the barrier for free rotation of the rare gas atom about the I2 molecule on the B-state potential. Ground-state binding energies of 16.6(6) and 16.3(6) cm-1 were determined for the T-shaped and linear conformers, respectively. These spectra are compared to those calculated using the experimentally determined rotational temperatures. Based on the agreement between the experimental and calculated spectra, the binding energies of the J'=0 states with 0 and 2-6 quanta of excitation in the He...I2 bending mode on the B state were determined. Several models for the B-state potential were used to investigate the origins of the shape of the contour of the higher-energy feature in the spectra for He...I2 and He...Br2. The shape of the contours was found to be relatively insensitive to the choice of potential. This leads us to believe that the spectra of these systems are relatively insensitive to the parameters of the B-state potential energy surface and are more sensitive to properties of the halogen molecule.
在氦超声速膨胀中，I₂的激光诱导荧光光谱和作用光谱已在I₂的B - X、20 - 0区域记录下来。光谱中识别出了两个特征。能量较低的特征源于在X态和B态势能上呈T形构象的态之间的跃迁。能量较高的特征反映了从X态上呈线性构象的态到能量大于稀有气体原子围绕B态势能上的I₂分子自由旋转势垒的态的跃迁。分别确定了T形和线性构象体的基态结合能为16.6(6)和16.3(6) cm⁻¹。将这些光谱与使用实验确定的转动温度计算得到的光谱进行了比较。基于实验光谱和计算光谱之间的一致性，确定了B态上具有0个以及2 - 6个He...I₂弯曲模式激发量子的J' = 0态的结合能。使用了几种B态势能模型来研究He...I₂和He...Br₂光谱中能量较高特征的轮廓形状的起源。发现轮廓形状对势能的选择相对不敏感。这使我们相信这些系统的光谱对B态势能面的参数相对不敏感，而对卤素分子的性质更敏感。
