^(14)N_(2)和^(15)N_(2)在解离通道N(^(2)D_(5/2,3/2))+N(^(2)D_(5/2,3/2))阈值以上光解离产物精细结构分支比N(^(2)D_(5/2))/N(^(2)D_(3/2))的测量  

Fine-Structure Branching Ratios N(^(2)D_(5/2))/N(^(2)D_(3/2))above Threshold N(^(2)D_(5/2,3/2))+N(^(2)D_(5/2,3/2))for ^(14)N_(2) and ^(15)N_(2)

作　　者：芦丽亚 蒋攀 程敏 高蕻 Liya Lu;Pan Jiang;Min Cheng;Hong Gao(Beijing National Laboratory for Molecular Sciences(BNLMS),Institute of Chemistry,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院化学研究所,北京分子科学国家研究中心,北京100190 [2]中国科学院大学,北京100049

出　　处：《Chinese Journal of Chemical Physics》2024年第2期264-270,I0102,I0103,共9页化学物理学报（英文）

基　　金：This work is supported by the National Natural Science Foundation of China(No.21973100 and No.22103090);the Program for Young Outstanding Scientists of Institute of Chemistry,Chinese Academy of Science,and Beijing National Laboratory for Molecular Sciences;Hong Gao is also supported by the K.C.Wong Education Foundation;Pan Jiang is supported by the China Postdoctoral Science Foundation(No.2020TQ0324).

摘　　要：精确测量解离产物的自旋-轨道耦合精细结构分支比对于进一步了解小分子的光解动力学具有十分重要的意义。本文利用真空紫外泵浦-真空紫外探测时间切片离子速度成像装置,测量了^(14)N_(2)的c4′1∑_(u)^(+)(v′=6)态和b′1∑_(u)^(+)(v′=21)态以及^(15)N_(2)的b′∑_(u)^(0)(=20)态和b′1∑_(u)^(+)(v′=20)态和b′1∑_(u)^(+)(v′=21)解离至通道N(2D_(5/2,3/2))+N(2D_(5/2.3/2))产物精细结构分支比N(2D_(5/2))/N(2D_(3/2)).实验结果表明,产物精细结构分支比N(2D_(5/2))/N(2D_(3/2))与^(14)N_(2)或^(15)N_(2)所在的转动能级无关而与其电子态和振动能级的性质有关。^(14)N_(2)的c4′1∑_(u)^(+)(v′=6)态和^(15)N_(2)的b′1∑_(u)^(+)(v′=20)态均接近解离通道N(2D_(5/2,3/2))+N(2D_(5/2,3/2))的阈值,产物精细结构分支比N(2D_(5/2))/N(2D_(3/2))数值均为-1.35;而^(14)N_(2)和^(15)N_(2)的b′∑_(u)^(+)(v′=21)态均远高于解离通道N(2D_(5/2,3/2))+N(2D_(5/2,3/2))的阈值,产物精细结构分支比N(2D_(5/2))/N(2D_(3/2))数值均为-1.00.本文猜测氮气在接近解离通道值时是一个遵循统计规律的解离过程,而在远高于解离通道阈值时是一个非绝热过程,这可能是本实验中观测到的产物精细结构分支比振动依赖现象的原因.要定量解释本实验的测量结果,需要在该解离通道阈值附近的氮气高精度势能曲线及其相互作用信息。Accurate measurements of the product spin-orbit fine-structure branching ratios are important for understanding the detailed photodissociationdynamics of small molecules.In this study,the atomic spin-orbit fine-structure branching ratio N(2D_(5/2))/N(2D_(3/2))to the dissociation channel N(2D_(5/2,3/2))+N(2D_(5/2,3/2))is measured for the c4′1∑_(u)^(+)(v′=6)and b′1∑_(u)^(+)(v′=21)states of ^(14)N_(2),and the b′1∑_(u)^(+)(v′=20)and b′1∑_(u)^(+)(v′=21)states of 15N2 by using the vacuum ultraviolet(VUV)-pump-VUV-probe time-sliced velocity-mapped ion imaging setup.The measurements show that the fine-structure branching ratio N(2D_(5/2))/N(2D_(3/2))is independent of the rotational level of the parent molecule(^(14)N_(2) or ^(15)N_(2))in each vibronic state,while it does show dependence on the vibronic characteristics.It is-1.35 for the c4'zt(u'=-6)state of ^(14)N_(2) and b′∑_(u)^(+)(=20)state of ^(15)N_(2),which are both close to the dissociation threshold N(2D_(5/2,3/2))+N(2D_(5/2,3/2));while it becomes~1.00 for the b′∑_(u)^(+)(=21)state of both 14N2 and 15N2,which are relatively far above the dissociation threshold.A possible change from a statistical process near the threshold to a diabatic process far above the threshold might have occurred to be responsible for the observed vibronic dependence of the branching ratio.Detailed informations on the potential energy curves and their mutual couplings near the dissociation threshold are highly desired for understanding the present experimental measurement.

关 键 词：精细结构分支比 真空紫外光 氮气分子 光解离动力学 科里奥利作用 

分 类 号：O562.4[理学—原子与分子物理]