Lifetime Measurements of Highly Charged Ions
Lifetime Measurements of Highly Charged Ions
复制标题
高电荷离子的寿命测量
DOI：
10.1238/physica.topical.100a00088
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发表时间：
2002
期刊：
影响因子：
2.9
通讯作者：
E. Bert
中科院分区：
文献类型：
--
作者：
E. Bert
由于守恒定律和对称性原理，当“正常”的电偶极子衰变到基态时，一个原子在激发态下“活”多久？然后发生了自旋变化的“相互结合”转变和电偶极“禁止”衰变，这对低密度日冕和地球等离子体的诊断很重要。高电荷态离子(皮秒和纳秒寿命范围)中的规则“允许”跃迁和组合间跃迁以前已经用直的、箔激发的、快的离子束测量过了。对于价层中只有一个或两个电子的离子，等电子序列的很长部分已经以这种方式被覆盖，产生了对跃迁速率的理论预测的实验测试，其结果好到几个百分点。最近，对于生命周期在毫秒范围内的情况来说，情况要比现在好得多。在这里，重离子存储环上的光学观测技术允许对相互结合和禁忌跃迁的原子寿命进行测量，精度通常好于1%，这显然超过了典型的传统离子陷阱数据的精度范围。电子束离子陷阱(EBIT)在“X射线”范围内表现出类似的精度，在一些光学跃迁测量中达到了几个百分点的不确定度。
How long does an atom "live" in an excited state, when due to conservation rules and symmetry principles the "normal" electric dipole decay to the ground state is forbidden? Then spin-changing "intercombination" transitions and electric- dipole "forbidden" decays occur that are important for the diagnostics of low-density solar coronal and terrestrial plasmas. Regular "allowed" and intercombination transitions in highly charged ions (picosecond and nanosecond lifetime range) have previously been measured with straight, foil-excited, fast ion beams. For ions with only one or two electrons in the valence shell, very long sections of the isoelectronic sequence have been covered this way, yielding experimental tests of theoretical predictions of transition rates that are good to a few percent. Recently the situation has become much better than this for lifetimes in the millisecond range. Here the technique of optical observation at a heavy-ion storage ring permits atomic lifetime measurements on intercombination and forbidden transitions with a precision that often is better than 1%, which is clearly surpassing the precision range of typical conventional ion trap data. The electron beam ion trap (EBIT) exhibits a similar precision in the "X-ray" range, and it has reached uncertainties of a few percent in some measurements of optical transitions.