N2O^＋离子B^2П态的光谱与光解离动力学  

Excitation Spectra and Photodissociation Dynamics of the B^2Π State of the N_2O^+ Ion

作　　者：孙中发[1] 高治[1] 吴向坤[1] 唐国强[1] 周晓国[1] 刘世林[1] 

机构地区：[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

出　　处：《物理化学学报》2015年第5期829-835,共7页Acta Physico-Chimica Sinica

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

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+(X2Π(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B2Π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B2Π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B2Π态带源的贡献,明确了N2O+离子B2Π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B2Π(v1,v2,v3)←X2Π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B2Π态的解离机理.N2O＋ions in the X^2Π（0,0,0） ground state were prepared by（3＋1） resonance-enhanced multiphoton ionization（REMPI） of jet-cooled N2 O molecules at 360.55 nm, and then photoexcited to various vibrational levels in the B^2Π 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 A^2Σ^＋ states were distinguished from the other bands, and the original band of B^2Π state was verified. The series of vibrational bands in the PHOFEX spectrum were assigned to the transition of B^2Π（v1,v2,v3） ←X^2Π. The average released kinetic energy of dissociation from the various B^2Π（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＋（B^2Π） were proposed with the aid of the theoretical potential energy surfaces of N2O＋ions.

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 

分 类 号：O644.1[理学—物理化学] O561.3[理学—化学]