Measurements of reaction dynamics of excited metastable atoms with molecules by using pseudorandom discharge

采用CCD探测器测量了亚稳态氦原子与靶分子碰撞产生的发射光谱。该方法大大缩短了测量时间，而且测量结果不受氦束强度漂移的影响。然而，由于宇宙射线引起的散粒噪声，测量时间被限制在5分钟以内。为了准备观测光谱，我们必须做以下步骤：（1）逐个消除散粒噪声，（2）添加几个数据文件，（3）校正每个像素的灵敏度。我们提出了一种新的算法来消除散粒噪声。在这项研究中，我们测量了高分辨率的NH NH_3靶产生的（A-X，c-a）谱，HCl/HBr靶产生的HCl^+（A-X）和HBr^+（A-X）谱，H_2S靶产生的SH^+（A-X）谱，并通过提高合成光谱与观测光谱比较的精度来实现对振转分布的确定。据此，首次发现了HCl^+（A，v '= 0）和HBr^+（A，v'= 0）的转动布居的双峰分布。通过分析在入射势面和出射势面上传播的波包，阐明了HCl^+（A，v '= 0）的转动激发。在这项研究中开发的方法可以适用于一般的电离和解离。

A CCD detector has been introduced to measure emission spectra produced by collisions of excited metastable helium atoms with target molecules. According to this method, the time spent has been remarkably reduced and the observed spectra are free from the drift of the intensity of helium beam. Nevertheless, the time for measurement was limited up to 5 minutes because of shot noises caused by cosmic ray. In order to prepare observed spectrum we have to do the following procedures : (1) elimination shot noises one by one, (2) addition a couple of data files, and (3) correction sensitivity for each pixel. We have developed a new algorithm to eliminate shot noises.In this study, we have measured with high resolution the NH(A-X, c-a) spectra produced from NH_3 target, the HCl^+(A-X) and HBr^+(A-X) spectra from HCl/HBr target, and the SH^+(A-X) spectra from H_2S target, and achieved to determine the rovibrational distributions by improving the accuracy for the synthetic spectrum that compares with the observed spectrum. Accordingly, bimodal distributions of the rotational populations for HCl^+(A, v'=0) and HBr^+(A, v'=0) have been found at first. The rotational excitation observed for HCl^+ (A, v'=0) has been clarified by analyzing the wave packet, which propagates on the incident and exit potential surfaces. The method developed in this study can be applied to ionization and dissociation in general.