Proposal and theoretical investigation with optimization for nuclear spin-polarization using intense laser pulses

使用强激光脉冲优化核自旋极化的提案和理论研究

基本信息

批准号：
14540262
负责人：
NAKAJIMA Takashi
金额：
$ 2.11万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

(1)We came to the idea that there may be a possibility to polarize electron-spin of residual ions if one can polarize spin of photoelectrons. Based on this assumption, we have pursued the possibility of the simultaneous production of spin-polarized electrons/ions upon photoionization. Alkaline-earth atoms are ideal for such investigation, and we have chosen Sr for a target atom. Two schemes are considered : The first one is one-photon resonant two-photon ionization, and the second one is one-photon resonant one-photon ionization. After the theoretical study, we have found that 66% spin-polarization is possible for the latter, while >90% spin polarization is possible for the former at the expense of more than few orders of magnitude smaller yield.(2)Based on the theoretical result in (1), we have performed experimental study, and obtained 64% spin-polarization as we expected. This experimental result is an important cornerstone toward the construction of a spin-polarized source.(3)In order to achieve a better performance as a spin-polarized source, it is essential to improve the degree of spin-polarization and yield. For that purpose, the use of autoionizing resonance seems to be a promising scheme. We have replaced a wavelength-fixed ionization laser (excimer laser) by a tunable dye-laser, and carried out experiments to find that the significant improvement of spin-polarization (64% to 78%) and two-orders of magnitude improvement in terms of yield. Furthermore, we have theoretically investigate a new scheme to polarize spin using short laser pulses.

(1)我们得出这样的想法：如果可以极化光电子的自旋，则可能有可能极化残留离子的电子自旋。基于这个假设，我们研究了光电离同时产生自旋极化电子/离子的可能性。碱土原子是此类研究的理想选择，我们选择 Sr 作为目标原子。考虑两种方案：第一种是单光子共振双光子电离，第二种是单光子共振单光子电离。经过理论研究，我们发现后者可以实现66%的自旋极化，而前者可以实现>90%的自旋极化，但代价是产量要小几个数量级。(2)基于(1)中的理论结果，我们进行了实验研究，得到了我们预期的64%的自旋极化。该实验结果为构建自旋极化源奠定了重要的基础。(3)为了获得更好的自旋极化源性能，必须提高自旋极化程度和产率。为此，使用自电离共振似乎是一个有前途的方案。我们用可调谐染料激光器代替了波长固定的电离激光器（准分子激光器），并进行了实验发现自旋偏振显着改善（64％至78％），并且在性能方面提高了两个数量级的产量。此外，我们从理论上研究了一种使用短激光脉冲偏振自旋的新方案。