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

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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.