本文研究了双光子共振相干激发三能级系统的问题。在两个超短激光脉冲具有相同波形的条件下,求出了双光子共振三能级系统的布洛赫(Bloch)方程组的解析解,求出了三能级系统能级集居数及激发速率的表示式,获得了粒子数完全反转以及获得最大激发速率的条件。采用平均场近似,求出了双光子离共振布洛赫方程组的解析解,导出了同位素相干选择激发系数的解析表达式,理论计算证明双光子共振相干激发具有很高的同位素选择性。

In this paper coherent excitation of two-photon resonance in three-level systems is discussed. Under the condition of two ultrashort pulses with the same waveform, analytical solution of Blochequations of two-photon resonance, level-population and expression of excitation rate in three-level systems have been derived. Conditions for full inversion of population and maximal excitation rate have been obtained. With average-field approximation, analytical solutions of Bloch equations of two-photon off-resonance have been obtained. The analytical expression of isotope coherent selective excitation coefficient has been deduced* Theoretical calculaiiioiis show that the coherent excitation of two-photon resonance has a very high Isotopic selectivity.