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MEASUREMENT OF CHARGE TRANSFER CROSS SECTION IN VERY LOW ENERGY REGION

极低能区电荷转移截面的测量

基本信息

批准号：
12640397
负责人：
SHIMIZU Tadao
金额：
$ 2.3万
依托单位：
Tokyo University of Science, Yamaguchi
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640397/
关键词：
atomic physics charge transfer collision ion trap laser cooling レーザー冷却衝突散乱断面積電荷移動 rfイオントラップ衝突散乱断面図 atomic physics collisional cross section charge transfer ion trap laser cooling frequency standards

项目摘要

The charge transfer process between a laser cooled magnesium ion and a thermal barium atom is successfully observed in a radio frequency ion trap in extremely low energy regime. The merit of ion trap experiment is that the generated ion is also trapped and very high sensitivity is achieved. The production of barium ion is confirmed by observing the laser-induced fluorescence from the ion.The cross section is estimated to be 10^<-4> nm^2. This well agrees with the value calculated from a theory in the reference (D. Rapp and W.E.Francis, J. Chem. Phys. 37, 2631(1962)).The charge transfer process allows us to achieve sympathetic cooling of various ions. The magnesium ion is easily cooled by a single laser, because its energy level structure is simple. The charge and "cold temperature" of magnesium ion are transferred to guest ions through collisions. We observed the temperature of sympathetically cooled barium ion of 500K, which is much smaller than that of the ion cooled by Helium buffer gas (4000K). We have calculated the limiting temperatures achieved by the sympathetic cooling as functions of ion temperatures and ion masses. The experimental confirmation of our theoretical model is achieved in a pair of magnesium and barium ions. The theory predicts that when the temperature of host ion is low the heavier guest ions are cooled more efficiently, while the guest ion temperature increases rapidly with increasing mass in higher temperature region. The resonant oscillation modes of sympathetically cooled ions in a radio frequency trap are also investigated through charge transfer process in the trap. Tow types of collective oscillation are observed. The frequency of oscillation can be calculated by a theoretical model, which agrees well with the observation. Irrelevant ions can be removed from the trap by applying an rf-voltage resonant to the proper frequency of the ions.

在极低能区的射频离子陷阱中，成功地观测到了激光冷却的镁离子和热的钡原子之间的电荷转移过程。离子陷阱实验的优点是产生的离子也被捕获，并获得了很高的灵敏度。通过观察离子的激光诱导荧光证实了该离子的产生，其截面估计为10^~(-4)nm~(-2)，这与文献(D.Rapp和W.E.Francis，J.Chem)的理论计算值很好地吻合。太棒了。(37,2631(1962))。电荷转移过程允许我们实现各种离子的共鸣冷却。镁离子的能级结构很简单，很容易被单一的激光冷却。镁离子的电荷和“冷温度”通过碰撞传递给客离子。我们观察到了对称冷却的钡离子的温度为500K，远低于氦缓冲气体冷却的离子的温度(4000K)。我们计算了共振冷却达到的极限温度作为离子温度和离子质量的函数。我们的理论模型在一对镁和钡离子中得到了实验验证。理论预测，当主体离子的温度较低时，较重的客离子被更有效地冷却，而在高温区，客离子的温度随着质量的增加而迅速升高。通过陷阱中的电荷转移过程，研究了射频陷阱中交感冷却离子的共振振荡模式。观察到了两种类型的集体振荡。振荡频率可用理论模型计算，与观测结果吻合较好。通过对离子的适当频率施加射频电压谐振，可以将不相关的离子从陷阱中移除。