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

我们研制了一种新的测量离子-极性分子冷反应速率的实验装置。首先，斯塔克速度滤光器是为产生慢极性分子而开发的。我们成功地产生了峰值速度为23~40m/S的Nd3、CH2O和CH3CN慢束，特别是首次实现了CH3CN慢束的产生。此外，还测定了慢分子数密度n=10^4~10^6 cm~(-3)，这是确定反应速率常数的重要参数。最后，测量了钙离子库仑晶体与慢极性分子的反应速率。反应速率约为10^-lt；-6&gt；-5-gt；S；-1&gt；，与典型的分子离子-极性分子在很低温度下的反应速率相比，这是非常慢的。这一事实表明，Ca~(2+)适合作为分子离子交感冷却的冷却剂，用于冷离子-极性分子反应的反应速率测量。这是本研究的一项重要成果。

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.