物理化学学报 >> 2015, Vol. 31 >> Issue (5): 829-835.doi: 10.3866/PKU.WHXB201503041

热力学,动力学和结构化学 上一篇    下一篇

N2O+离子B2П态的光谱与光解离动力学

孙中发, 高治, 吴向坤, 唐国强, 周晓国, 刘世林   

  1. 中国科学技术大学化学物理系, 合肥微尺度物质科学国家实验室(筹), 合肥230026
  • 收稿日期:2015-01-05 修回日期:2015-03-03 发布日期:2015-05-08
  • 通讯作者: 周晓国 E-mail:xzhou@ustc.edu.cn
  • 基金资助:

    国家自然科学基金(21373194)和国家重点基础研究发展规划项目(973) (2013CB834602)资助

Excitation Spectra and Photodissociation Dynamics of the B2П State of the N2O+ Ion

SUN Zhong-Fa, GAO Zhi, WU Xiang-Kun, TANG Guo-Qiang, ZHOU Xiao-Guo, LIU Shi-Lin   

  1. Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, P. R. China
  • Received:2015-01-05 Revised:2015-03-03 Published:2015-05-08
  • Contact: ZHOU Xiao-Guo E-mail:xzhou@ustc.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21373194) and National Key Basic Research Program of China (973) (2013CB834602).

摘要:

用一束波长为360.55 nm的激光直接作用于超声射流的N2O分子束, 通过(3+1)共振增强多光子电离(REMPI)过程制备纯净的N2O+(X2П(0,0,0))母体离子, 再用另一束波长在243-278 nm范围的激光将母体离子激发至B2П态后解离. 扫描解离激光波长, 监测NO+离子碎片的强度, 从而获得N2O+离子B2П态的光致碎片激发(PHOFEX)谱. 通过拟合转动分辨光谱, 得到了相应的转动常数和自旋分裂常数, 从而区分了A2Σ+态高振动能级和B2П态带源的贡献, 明确了N2O+离子B2П态的光谱"带头"位置(37154 cm-1), 并将获得的振动光谱初步归属为B2П(v1,v2,v3)←X2П的振动跃迁序列. 通过对NO+碎片离子的飞行时间质谱峰形的分析, 还获得了解离过程中释放的平均平动能, 并结合电子激发态势能面, 讨论了N2O+离子B2П态的解离机理.

关键词: N2O+离子, 共振增强多光子电离, 振动光谱, 飞行时间质谱, 光解离

Abstract:

N2O+ ions in the X2П(0,0,0) ground state were prepared by (3+1) resonance-enhanced multiphoton ionization (REMPI) of jet-cooled N2O molecules at 360.55 nm, and then photoexcited to various vibrational levels in the B2П state over a wavelength range of 243-278 nm, followed by dissociation. The photofragment excitation (PHOFEX) spectrum was recorded by measuring the intensity of NO+ ion fragments vs excitation wavelength. The rotational constants and spin-orbit coupling were obtained by fitting the rotational structures of the vibrational bands. Thus, the contributions of highly excited vibronic levels of A2Σ+ states were distinguished from the other bands, and the original band of B2П state was verified. The series of vibrational bands in the PHOFEX spectrum were assigned to the transition of B2П(v1,v2,v3) ←X2П. The average released kinetic energy of dissociation from the various B2П(v1,v2,v3) ionic states was obtained by fitting the spreading contour of the NO+ ion peak in time-of-flight mass spectra. Dissociation mechanisms of N2O+(B2П) were proposed with the aid of the theoretical potential energy surfaces of N2O+ ions.

Key words: N2O+ ion, Resonance enhanced multiphoton ionization, Vibrational spectroscopy, Time-of-flight mass spectrum, Photodissociation

MSC2000: 

  • O644.1