Algebraic solution for a two-level atom in radiation fields and the Freeman resonances (14 pages)
Algebraic solution for a two-level atom in radiation fields and the Freeman resonances (14 pages)
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DOI：
10.1103/physreva.73.023419
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发表时间：
2005-09
影响因子：
2.9
通讯作者：
D. Guo;Yong-Shi Wu;L. V. Woerkom
中科院分区：
文献类型：
--
作者：
D. Guo;Yong-Shi Wu;L. V. Woerkom
利用复分析的代数方法，精确地求解了二能级原子与单色光场相互作用时的波动方程。得到了准能量的封闭表达式，表明无论原始电平间距还是移位电平间距是驱动频率{ω}的整数倍，Bloch-Siegert位移都是有限的。我们还发现，当原始能级间距是{ω}的整数倍时，波函数虽然是有限的，但当强度相关的移位能量间距是光子能量的整数倍时，波函数变得发散。这一结果为阈值以上电离实验中观察到的弗里曼共振的发生提供了从头算理论解释。
Using techniques of complex analysis in an algebraic approach, we solve the wave equation for a two-level atom interacting with a monochromatic light field exactly. A closed-form expression for the quasienergies is obtained, which shows that the Bloch-Siegert shift is always finite, regardless of whether the original or the shifted level spacing is an integral multiple of the driving frequency {omega}. We also find that the wave functions, though finite when the original level spacing is an integral multiple of {omega}, become divergent when the intensity-dependent shifted energy spacing is an integral multiple of the photon energy. This result provides an ab initio theoretical explanation for the occurrence of the Freeman resonances observed in above-threshold ionization experiments.