Reaction dynamics of metastable helium molecules and atoms near 4.2 K.
Reaction dynamics of metastable helium molecules and atoms near 4.2 K.
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4.2 K 附近亚稳态氦分子和原子的反应动力学。
DOI：
10.1103/physreva.48.364
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Hunt
中科院分区：
文献类型：
--
作者：
Tokaryk;Brooks;Hunt
先前用脉冲质子束[R]辐照4.2 K附近的致密氦气获得了亚稳氦原子（2[ital s] [sup 3][ital s], 2[ital s] [sup 1][ital s]）和分子（[ital a][sup 3][Sigma][sub [ital u]][sup +]）的红外吸收光谱。L.布鲁克斯，J. L.亨特，D. W.托卡里克，J.化学。物理学报，1999,14(4):559 - 564。分子光谱是不寻常的，因为在[ital a][sup 3][Sigma][sub u][sup +]状态下观察到的旋转振动分布远未达到热平衡。观察到三种不同的旋转振动基团：(i) [ital v]=0, [ital N]=1（热分子）；（ii） [ital v]= 0,9 [le][ital N][le]21（旋转激发分子）；（iii） 10[le][ital v][le]12, [ital N]=1（振动激发分子）。在这项工作中，研究了这三个分子群成员在照射期间和随后的余辉中的时间演变。此外，还研究了2[ital s] [sup 3][sup s]—2[sup 3][sup p] [sup 3][sup p]原子线的演化。本研究定量地探讨了亚稳分子在4.2 K附近气相的反应动力学。气体压力在100到750托之间。用瞬态数字化系统采集了时间分辨数据，并对脉冲质子束的几千个周期进行了求和。利用理论跃迁矩将吸收测量值转换为时间分辨数密度。分析要求用非线性最小二乘拟合程序将数据拟合到一组耦合微分方程的解上。结果提供了对产生异常分子分布的复杂反应的深入了解，以及亚稳分子、亚稳原子和背景氦气之间的反应。«少
Infrared absorption spectra from metastable helium atoms (2[ital s] [sup 3][ital S], 2[ital s] [sup 1][ital S]) and molecules ([ital a] [sup 3][Sigma][sub [ital u]][sup +]) were previously acquired by irradiating dense helium gas near 4.2 K with a pulsed proton beam [R. L. Brooks, J. L. Hunt, and D. W. Tokaryk, J. Chem. Phys. 91, 7408 (1989)]. The molecular spectrum was unusual because the observed rovibrational distribution within the [ital a] [sup 3][Sigma][sub u][sup +] state was far from thermal equilibrium. Three different rovibrational groups were observed: (i) [ital v]=0, [ital N]=1 ( thermal'' molecules); (ii) [ital v]=0, 9[le][ital N][le]21 (rotationally excited molecules); and (iii) 10[le][ital v][le]12, [ital N]=1 (vibrationally excited molecules). In this work, the time evolutions of members of these three molecular populations were studied both during irradiation and in the subsequent afterglow. In addition, the evolution of the 2[ital s] [sup 3][ital S]--2[ital p] [sup 3][ital P] atomic line was investigated. This study quantitatively explores the reaction dynamics of the metastable molecule in the gas phase near 4.2 K. Gas pressures between 100 and 750 Torr were used. Time-resolved data were taken with a transient-digitizer system and summed for several thousand cycles of the pulsed protonmore » beam. The absorption measurements were converted to time-resolved number densities with the aid of theoretical transition moments. The analysis required that the data be fit to the solutions of sets of coupled differential equations with a nonlinear least-squares-fit routine. The results provide insight into the complicated reactions involved in generating the unusual molecular distribution and into the reactions between the metastable molecules, metastable atoms, and the background helium gas.« less