摘要：
Collisional deactivation rate constants,k 5 (M)for HBr(Χ1Σ+ν″=5)by M= H 2 ,N2 ,CO2 ,and HBr were obtained u-sing the degenerated stimulated hyper-Raman (OSHR)pumping method in a pumping-probe configuration.High- resolution transient laser induced fluorescence (LIF)was used to detect collisionally relaxed HBr.For M=CO2 ,an efficient near-resonant 1-1 vibration-to-vibration (V-V )energy exchange was observed.It appeared that the presence of a strong infrared-active vibra-tional mode was a favorable situation for an efficientV-V energy transfer.A 1-1 resonance exciting the infrared forbidden N2 (1←0)vibration was also observed,but it was 2 orders of magnitude smaller than that of CO2 .Self-relaxation rate constants of HBr (ν″=5)were measured.Single quantum relaxation accounted for about 70% of the total relaxation out of stateν″=5,and two-quantum relaxation made contributions (25%)to the vibrational relaxation at this vibrational energy.Direct evidence for 2-1 res-onance in HBr (ν″=5)+H 2 was observed.Initial preparation of HBr (ν″=5)resulted in nearly no population in HBr (ν″=4), but direct population of HBr (ν″=3).Therefore only 2-1 resonant energy transfer was important for H 2 relaxation.The state specific rate constant for HBr was obtained by the analysis of the state-to-state relaxation data.It was found that the data could be fitted with one adjustable normaligation parameter using a single-quantum relaxation model,which restricted the rate con-stant.A strong mass effect on the vibrational relaxation rate constant was observed.A further check of the character of the V-V resonant energy transfer in highly vibrationally excited HBr was the temperature dependence of the rate constants.For M=CO2 , the temperature dependence of the 1-1 near-resonant energy transfer rate constats was found to be inverted.In contranst,the temperature dependence of the relaxation rate constants for M= H 2 and HBr was normal.For M=N2 ,a weak but position tem-perature dependence was found.It suggested that this resonance occurred by a different mechanism compared with that in CO2 .%利用简并受激超拉曼泵浦激发HBr(Χ1Σ+ν″=5)振动态,由高分辨瞬时激光感应荧光(LIF)探测碰撞弛豫后HBr(ν″≤5)各振动态时间分辨布居数的演化过程,得到了HBr(ν″=5)分别与分子M(H 2,N2,CO2和HBr)的碰撞弛豫速率系数.对于M=CO2,近共振的1-1振动-振动(V-V)能量转移是有效的,这一结果表明CO2强的红外振动模对近共振V-V能量转移是有利的.而红外禁戒跃迁的N2(0-1)的近共振V-V转移虽然也能观察到,但相应速率系数比CO2小2个量级.碰撞分子的振动跃迁红外活性越强,能量转移速率系数越大.在HBr(ν″=5)+HBr的自弛豫过程中,单量子弛豫率占总弛豫率的70%,而双量子弛豫约占25%.在HBr(ν″=5)+H 2中,只有2-1的V-V近共振过程是重要的.同时还研究了V-V近共振能量转移速率系数与温度变化的关系,对于CO2的1-1近共振,V-V能量转移速率系数随温度的增加而减小;对于H 2和HBr,其弛豫速率系数随温度的增加而增加;对于N2,其弛豫速率系数随温度的增加而缓慢增加.
