六极杆电场对CH_3X(X=Cl,Br,I)分子转动态的选择和聚焦

The Rotational State-Selected and Focus of CH_3X( X = Cl,Br,I) in Hexapole Field

分析了六极杆电场对对称陀螺分子转动态选择和聚焦的原理,采用Monte Carlo方法模拟了CH_3X(X=Cl,Br,I)分子在六极杆电场中聚焦曲线,获得了单一转动态的分子;通过比较一阶Stark效应和二阶Stark效应对分子聚焦曲线的影响,得到了考虑二阶Stark效应必要性的条件;以CH_3I分子|JKM>=|111>转动态为例,讨论了六极杆尺寸及载气对聚焦曲线的影响.模拟结果表明:可以为六极杆态选择和分子的取向实验装置设计及研究提供重要的参考.

We analyze the principle of rotational state-selected and focus of symmetric top molecules in hexapole field. We use Monte Carlo method to simulate the focus curves of CH_3X( X = Cl,Br,I) molecules,which show that the single quantum rotational state of molecule is acquired after passing the hexapole. By comparing the affects of first-order Stark effect and the second-order Stark effect on focus curves of CH_3X( X = Cl,Br,I),the conditions of the necessity of considering second Stark effect is obtained. We also discuss the influences of hexapole size and carrier gas on focusing curve in the case of CH_3I molecule with | JKM > = | 111 > rotational state. Our results provide important reference for setup design and study of state-selected and orientation in experiment.