Isotope Separation by Lasers

与激光同位素分离、激光技术的发展、激光与原子/分子的相互作用和光离原子的收集有关的研究已经开展。1)在激光技术方面，利用硅晶闸管和两级磁脉冲压缩器成功研制了大口径铜蒸汽激光器（CVL）的全固态开关。由于没有氢闸流管开关，CVL电源的使用寿命大大提高。2)对激光与原子相互作用中使用频率啁啾激光的绝热快速通过方案进行了分析和实验研究。从频率扫描速度和峰值激光强度两个方面估计了实现完全人口反演的条件。实验数据与分析结果吻合较好。3)研究了两种不同颜色激光脉冲在共振三能级介质中的传输。通过对三能级Bloch-Maxwell方程的数值求解，分析了激光脉冲形状和原子居数随时间的变化。观察到脉冲延迟和脉冲破裂，特别是在第一次激发激光脉冲。结果表明，电离效率的迅速降低是由两个激光脉冲的分离引起的。提出了一种新的测量金属原子电荷转移截面的交叉光束技术。一个原子束通过激光光电离产生的脉冲离子束与第二个原子束碰撞。在10-1000eV范围内，测量了Gd、Y和U的电荷转移截面随冲击能的变化。实测值与用简单的解析模型理论预测值相比是相当大的。

Related to the laser isotope separation, developments of laser technologies, researches on laser-atom/molecule interaction and collection of photoionized atoms have been performed.1) In laser technology, all solid state switches for large-bore copper vapor laser (CVL) have been successfully developed by using SI thyristors and two-stage magnetic pulse compressers. Without hydrogen thyratron switches, the life of CVL power supply was greatly improved.2) In laser-atom interaction, the adiabatic rapid passage scheme by using a frequency chirped laser has been investigated analytically and experimentally. The conditions to achieve complete population inversion were estimated with respect to the frequency scanning velocity and the peak laser intensity. The experimental data show a fairly good agreement with the analytical ones.3) The propagation of two-different-color laser pulses in the resonant three-level medium has been studied. The three-level Bloch-Maxwell equations were solved numerically to analyze the change of the laser pulse shapes and the timevarying atomic populations. The pulse delay and pulse break-up were observed especially for the first excitation laser pulse. It is shown that the rapid decrease of the ionization efficiency is caused by the separation of the two laser pulses.4) A new cross-beam technique has been developed to measure the charge transfer cross sections of metallic atoms. A pulsed ion beam produced from one atomic beam by laser photoionization was collided with the second atomic beam. The charge transfer cross sections of Gd, Y and U have been measured as a function of impact energy in the range of 10-1000eV. The measured values are fairly large compared with the theoretically predicted ones by using a simple analytical model.