A study of cold ion-molecule reactions between ionic Coulomb crystals and slow polar molecules

点击翻译按钮获取中文摘要

We have developed a new experimental apparatus to measure the reaction rates of cold ion-polar molecule reactions. First, the Stark velocity filter was developed for the generation of slow polar molecules. We have successfully produced slow ND_3, CH_2O, and CH_3CN beams with a peak velocity of 23～ 40 m/s. In particular, the generation of slow CH_3CN beam was carried out for the first time in this study. In addition, the number density of slow molecules was determined to be n=10^4～ 10^6 cm^<-3>, that is an important parameter to determine the reaction rate constant. Finally, the reaction rates between the Ca^+Coulomb crystals and the slow polar molecules were measured. The reaction rates are of the order of 10^<-6>～ 10^<-5> s^<-1>, which are very slow compared to a typical reaction rate of a molecular ion-polar molecule reaction at very low temperatures. This fact show that Ca^+is suitable for a coolant of sympathetic cooling of molecular ions, which are supplied for performing the reaction-rate measurements of cold ion-polar molecule reactions. This is an important achievement of this study.