缓冲气体冷却是将离子阱中的离子云冷却的最有效和实用的方法,缓冲气体的种类和数量是汞离子微波频标实验的关键技术.通过在马修方程中引入阻力项的方法,研究了线型离子阱中氦气、氖气、氩气对囚禁的汞离子的冷却效果,结果表明在氩气中汞离子运动的衰减时间最短.研究了为使钟跃迁(40.5 GHz)的频率移动最小,所需氦气的压强为10-5 Torr,氖气的压强为2.4×10-5 Torr.考虑到缓冲气体对汞离子的冷却效率和对气体压强的敏感性,氖气要比氦气、氩气更适合作缓冲气体.
Buffer gas cooling is the most effective and practical method to cool ions in ion trap.The kind and quantity of buffer gas are the key technologies in mercury ion microwave frequency standard experiments.Buffer gas made of helium,neon or argon was studied to cool trapped mercury ions (199Hg+)in a linear ion trap by introducing a resistance term in Mathieu's equation.It's found that the decay time of motion of 199Hg+ in argon gas is the shortest,and the frequency shift of the clock transition (40.5 GHz)is minimum when the pressure of helium is 10-5 Torr or the pressure of neon gas is 2.4 x 10-5 Torr.Neon is the most suitable buffer gas among helium,neon and argon,considering the decay time-constant of motion of 199Hg+ in buffer gases and 199Hg+ clock transition shift's sensitivity to the change of the pressure of buffer gas.
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