CF_3I在238 nm的光解碎片平动能谱研究:CF_3光解碎片的振动态分布和势能曲线交叉穿越几率  

Photofragment Translational Spectroscopy of CF_3I at 238 nm:Vibrational Distribution of CF_3 Fragments and Curve Crossing Probability

作　　者：林丹 程敏 杜宜奎 朱起鹤[1] LIN Dan;CHENG Min;DU Yikui;ZHU Qihe(Belting National Laboratory for Molecular Sciences,State Key Laboratory of Molecular Reaction Dynamics Institute of Chemistry,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Belting 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实验室分子反应动力学国家重点实验室,北京100190 [2]中国科学院大学,北京100049

出　　处：《高等学校化学学报》2018年第8期1713-1720,共8页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:21203207;21173236)资助~~

摘　　要：利用高分辨弱电场加速型光解碎片平动能谱仪,对CF3I在238 nm的光解动力学进行了研究.结果表明,来自3Q0平行跃迁的I*通道[CF3I(X)hν→‖CF3I(3Q0)→CF3(ν1,ν2)+I*],信号最强,并可以分辨出碎片CF3(ν1,ν2)的振动峰.通过对峰间距的分析,可以基本分辨出同时具有CF3碎片的振动波带CF3(ν1,ν2=0)与CF3(ν1,ν2=1).其中ν1=701 cm-1为对称伸缩振动,ν2=1086 cm-1为CF3伞形振动.测量了这些振动态的分布及振动波带分配比为∑P(ν1,1)/∑P(ν1,0)=0.48/0.52.还测得238 nm处4个光解通道的分支比:通道1(X→3Q0→I*)为0.664,通道2(X→3Q0→1Q1→I)为0.084,通道3(X→1Q1→I)为0.178,通道4(X→1Q1→3Q0→I*)为0.074.实验结果表明,3Q0→1Q1过程中的势能曲线交叉穿越几率P0→1=0.112,1Q1→3Q0过程中P1→0=0.294;I*通道的各向异性参数β(I*)=1.70,I通道β(I)=-0.04.The photodissociation dynamics of CF3 I at 238 nm was studied using our high resolution mini-TOF（ time of flight） photofragment translational spectrometer. The results indicated the strongest signal comes from the I＊channel of the3 Q0 parallel transition[i.e.,CF3 I（ X） →CF3 I（3 Q0） →CF3（ ν） ＋ I＊],and the vibrational peaks of CF3 fragments were resolved. From the peak gap,both the overtone bands（ ν1,ν2= 0） and the combination bands（ ν1,ν2= 1） of CF3 fragments were partially resolved（ ν1= 701 cm-1,the symmetric stretch mode; ν2= 1086 cm-1,the umbrella mode）. At 238 nm,the ratio of the two band series was found with∑P（ ν1,1）/∑P（ ν1,0） = 0. 48/0. 52. The vibrational distribution of CF3 fragments were also measured. The branching fractions of the four pathways were 0. 664 for X→3 Q0→ I＊,0. 084 for X→3 Q0→1 Q1→I,0. 178 for X→1 Q1→I and 0. 074 for X→1 Q1→3 Q0→I＊. The experimental curve crossing probability for3 Q0→1 Q1 was P0 → 1= 0. 112 and that for1 Q1→3 Q0 was P1→0= 0. 294. The anisotropy parameter of I＊channel was β（ I＊） =1. 70,and that of I channel was β（ I） =-0. 04.

关 键 词：光解 三氟碘甲烷 光解碎片平动能谱 振动态激发 势能曲线交叉穿越几率 

分 类 号：O643[理学—物理化学]