振动态选择的NO+2离子e3B2态解离生成氧离子通道的动力学

摘要

结合最新的阈值光电子—光离子符合速度成像技术和同步辐射光电离,开展了振动态选择的NO+2离子e3B2态解离动力学研究.在18.8-19.2 eV范围内获得的NO+2离子e3B2态的振动分辨阈值光电子谱与前人结果基本符合,而由e3B2态(0,0,0)和(1,0,0)振动能级解离生成的O+碎片离子的符合速度成像清楚地显示出多个圆环结构,表明解离过程中生成了多种具有不同速度的O+离子,对应中性解离碎片NO分子处于不同的内态.通过速度和角度积分,我们分别获得了解离过程中释放的总平动能分布和O+离子的角度分布,其中两振动态选择的NO+2离子解离生成的NO分子x2n态振动分布十分相似,主要布居的振动量子数为3-5.解离释放的可资用能近似平均分配到碎片的平动能和内能,其中碎片总平动能约占52％,内能约占48％.此外,O+离子的各向异性参数β约为0.3,且不随NO(X∏)振动量子数而剧烈变化.%The dissociation dynamics of vibrational state-selected NO2+ (e3B2) was investigated using threshold photoelectron-photoion coincidence velocity imaging and photoionization by synchrotron radiation. The vibrational resolution threshold photoelectron spectrum of NO2+(e3B2) was recorded in the energy range of 18.8-19.2 eV and was consistent with previous measurements. Furthermore, the coincident velocity images of the O+ fragments that dissociated from the (0,0,0) and (1,0,0) vibronic levels of NO2+(e3B2) showed a multi-ring structure, indicating that O+ fragments with different speeds were produced during dissociation as well as corresponding NO molecules with different internal energy distributions. The total kinetic energy released distributions and the angular distributions of O+ during dissociation were obtained subsequently from the images. The internal energy distributions of the NO (X2∏) fragments that dissociated from the two vibrational states of NO2+(e3B2) were very similar and consisted of 3-5 dominant populated vibronic levels. The available energy released from dissociation was found to be almost evenly distributed between the kinetic and internal energies of the fragments and, specifically, a total kinetic energy of 52% and an internal energy of 48% were obtained. In addition, the anisotropy parameter, β, of the O+ fragments was about 0.3 and was hardly dependent on the vibrationai quantum number of the NO(X2∏) fragment.