I_2(X^1∑_g^+)分子在脉冲射流中的振动弛豫

Vibrational Relaxation of I_2(X^1 ∑g^+) Molecule in Pulsed Supersonic Jet

本文利用激光诱导荧光时间分辩光谱技术,测量了I_2(X^1)分子在He及Ar载气脉冲射流中振动温度随时间的变化关系。实验结果表明,I_2分子振动态是非玻尔兹曼布居的,振动温度约经过300μS达到稳定值,通过一段平滑变化后,振动温度又开始升高。振动温度的整个变化过程与脉冲气流的建立过程相似,可以将其分为稳态和非稳态两个过程。利用“突然冷凝”模型,得到了I_2(X^1)分子v″=1及v″=2振动态的弛豫截面。

LIF time-resolved spretroscopy technique has been employed to determine the vibrational temperature of I_2(X^1∑_g^+)molecule in He and Ar pulsed supersonic jets. Measurements were carried out for stagnation pressure in the range of 400～1300 Torr. In genearl non-Boltzmann vibrational population distributions were found, characterized by the unequal pair-state vibrational temperatures of I_2(X^1∑_g^+) molecule. The pair-state vibrational temperatures drop to their steady value in 300μs, and they rise again about 900μs later. The whole variation process of vibrational temperature is quite similar to that of the gas pulse pressure, which can be devided into two kinds of processes--the steady and unsteady. Furthermore, the vibrational relaxation cross sections of I_2(X^1∑_g^+) at V^(?)=1 and v^(?)=2 states were also obtained, based on the 'sudden freeze' model.