与HBr（Χ1Σ+v″=1,J″=12）碰撞的CO2（0000）转动态分布

Nascent rotational distribution for CO2（0000, J） states from collisions with excited HBr (Χ1Σ+v″=1, J″=12)

利用受激拉曼泵浦激发HBr分子至Χ1Σ+(1,12)激发态,由相干反斯托克斯-拉曼散射(CARS)光谱确定分子的激发.通过测量CARS谱相对强度,得到了HBr分子Χ1Σ+态(1,12)能级的布居数密度为n1=0.54×10^13 cm^-3.在一次碰撞条件下,测量碰撞前后CO2(0000,J)态的激光感应荧光强度比,得到CO2转动态的双指数分布.由二分量指数拟合得到Ta=261 K的低能分布和Tb=978 K的高能分布.结果表明,碰撞后约有65%的分子处于低J态,属于弹性或近弹性的弱碰撞;约有35%的分子处于高J态,属于非弹性的强碰撞.在振动-转动平动(V-RT)能量转移过程中,CO2(0000,J)态的总出现速率系数为(1.3±0.3)×10^-10 cm^3 molecule^-1s^-1;低转动态的平均倒空速率系数为(2.9±0.8)×10^-10 cm^3 molecule-1s-1.总的出现速率系数比平均倒空速率系数小,但在量级上保持一致.对CO2 J=60-74高转动态,随着J值的增加,质心平移温度和质心平移能的平均改变增加.对低转动态,在碰撞过程中,J态既可能出现也可能被倒空,平移能的改变不易确定.

Rotationally state selective excitation of HBr(Χ1Σ+v″=1,J″=12)was achieved by stimulated Raman pumping.The full state-resolved distribution of scattered CO2(0000,J)molecules from collisions with excited HBr(E)was reported.The Coherent Anti-Stokes Raman Scattering(CARS)spectral technique was used to measure the density of HBr(1,12),and the value is 0.54×10^13cm^-3.Under single-collision conditions,nascent rotational distribution for scattered CO2(0000,J)was measured using high-resolution transient laser induced fluorescence(LIF)spectroscopy.The data yield the full state-resolved distribution of scattered CO2(0000).The scattered CO2(0000,J)molecules have a biexponential rotational distribution.Fitting the data with a two-component exponential model yields a low-energy distribution with Ta=261 K and a high-energy distribution with Tb=978 K.The cooler distribution accounts for 65%of the scattered population and results from elastic or weakly inelastic collisions that induce little rotational excitation in CO2.The hotter distribution involves large changes in CO2 rotational energy and accounts for 35%of collisions and results from strongly inelastic collisions that induce big rotational excitation in CO2.The value of total rate constant for appearance of scattered CO2(0000,J)is(1.3±0.3)×10^-10cm^3 molecule-1s-1.We have obtained a collisional average rate of kdep=(2.9±0.8)×10^-10cm^3 molecule-1s-1 by the population depletion measurements.The total appearance rate coefficient is smaller than the average depletion rate coefficient,but they remain the same in order of magnitude.For scattered CO2(0000,J=60-74)highly-rotational states,the average change of center of mass translation temperature and center of mass translation energy increase with the increase of J value.For CO2(0000)lower-rotational states,the change of translation energy is difficult to determine.