CO_2在与高振动激发NaH碰撞中的量子态分辨能量再分配

利用简并受激超拉曼泵浦激发NaH基态到高位振动态(ν″=14,J″=20)。研究了NaH(14,20)与CO_2(00°0)间的振转能量转移。利用吸收系数和瞬时Doppler线宽,得到不同池温下NaH(14,20)分子密度,测量CO_2(00°0,J)与NaH高振动态碰撞前后的瞬时泛频激光感应荧光谱线的相对强度,确定了CO_2(00°0,J=2~80)的初生态布居,它们呈现双指数转动分布。拟合实验数据得到两个转动温度T_(rot)=(650±80)和(1 531±150)K。较冷的分布约占CO_2(00°0)的79%,它是由弹性或弱非弹性碰撞产生的,因而CO_2只有很小的转动激发。另有21%的CO_2(00°0)较大地增加了转动能,故有较热的转动温度。对碰撞产生的CO_2(00°0,J)进行高分辨率瞬时泛频荧光谱线的轮廓测量,得到各转动态平移能的改变。对于CO_2(00°0,J=56~80),转移能从582cm~(-1)(对于J=60)增加到2 973cm~(-1)(对于J=80)。探测转动态布居数的改变,得到各转动态的产生速率系数k_(app)~J之和为(7.2±1.8)×10~(-10) cm~3·mol~(-1)·s~(-1),而平均倒空速率系数〈kdep〉=(6.9±1.7)×10~(-10)cm~3·mol~(-1)·s~(-1)。

Quantum State-Resolved Energy Redistribution of CO2 from Collisions with Highly Vibrationally Excited NaH

Degenerate stimulated hyper-Raman pumping is used to excite high vibrational states of NaH.The full state-resolved distribution of scattered CO2 (000 0,J)molecules from collisions with excited NaH(ν″=14,J=21)was reported.The nascent number densities of NaH were determined from absorption measurements at times t=1μs as the laser to prepare NaH(ν″,J″). Absorption signals were converted to NaH(ν″,J″)population using absorption coefficients and the transient Doppler-broadened linewidths.The nascent CO2 (000 0,J)population were obtained from transient overtone laser induced fluorescence line intensity measured at short times relative to the time between collisions.The scattered CO2 (000 0,J=2~80)molecules had a biexponen-tial rotational distribution.Fitting the data with a two-component exponential model yielded CO2 product distributions with Trot=(650±80)and (1 531±150)K.The cooler distribution accounted for 79% of the scattered population and resulted from elas-tic or weakly inelastic collisions that induced very little rotational excitation in CO2 .The hotter distribution involved large chan-ges in CO2 rotational energy and accounted for 21% of collision.Nascent translational energy profiles for scattered CO2 (000 0,J=60~80)were measured using high resolution transient overtone fluorescence.The relative translational energy of the scattered molecules increased as a function of final CO2 rotational state with〈ΔErel〉=582 cm-1 for J=60,and 2 973 cm-1 for J=80.En-ergy transfer rates were determined for the full J-state distribution by monitoring the change of the nascent population.The total rate constant for appearance of scattered CO2 (000 0)was kapp=(7.2±1.8)×10-10 cm3 ·mol-1 ·s-1 .The depletion for the low-J CO2 states was involved in the collisional energy transfer of the initial distribution.For J=2~38,the average rate constant for depletion of scattered CO2 (000 0)is 〈kdep〉=(6.9±1.7)×10-10 cm3 ·mol-1 ·s-1 .