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

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.