Laser spectroscopy and application of condensed hyperpolarized noble-gas using synchrotron radiation and MRI.

在这个项目中，我们打算使用同步辐射和磁共振成像的超极化惰性气体原子的激光光谱学。高功率半导体激光器的窄化将实现核自旋的有效极化。我们认为，通过研究惰性气体原子与介质或磁性表面的相互作用，发展了一种新的核极化方法，并研制了低频（10 kHz - 10 MHz）磁共振装置，用于探测低场（10 mT）下核自旋的共振信号。利用Rb原子的光抽运，可以探测到气相Rb原子1%的偏振态。利用去年研制成功的高功率半导体激光器的窄化效应，我们可以获得高偏振度的光子和角动量的有效转移。激光功率为2 W，比以前报道的值弱10倍。今年，我们稳定了激光频率，并通过广域激光阵列放大了窄激光。这种激光系统保证了超极化惰性气体的高效率生产。通过去除Rb原子，检测到0.1%的极化。由于纯Rb原子有可能获得更高的极化度，因此我们需要找到Rb原子无损转移的条件，以检测Rb原子与介质表面的相互作用.我们报道了致密Rb原子的电子自旋动力学，它强烈地依赖于极化度、磁场、原子密度和射频场的脉冲面积.本文从实验和理论上证明了原子相干性的衰减是由于稠密Rb原子的自旋交换相互作用。

In this project we intend the laser spectroscopy of hyperpolarized noble-gas atoms additionally using synchrotron radiation and magnetic resonance imaging. The efficient polarization of nuclear spin will be achieved by the narrowing of high power laser diode. We believe that the novel method of nuclear polarization is developed by studying the interaction of noble-gas atoms with dielectric or magnetic surface.To detect the resonance signal of nuclear spins at low field (10 mT) we developed the equipment of low frequency (10 kHz - 10 MHz) magnetic resonance. By the optical pumping of Rb atoms, the polarization at 1 % could be detected for gas phase Xe atoms. We can obtained the high polarization and the efficient transfer of angular momentum from photon to Xe atom by the narrowing of high power laser diode, developed last year. The laser power is 2 W, and ten times weaker than the previously reported values. This year we stabilized the laser frequency and amplified the narrowed laser by the broad area laser array. This laser system promises the high efficiency of production of hyperpolarized noble gases. By removing Rb atoms, the polarization at 0.1 % is detected. It is possible to obtain the higher polarization for pure Xe gas, so we need to find the condition of lossless transfer of Xe atoms in order to detect the interaction with dielectric surface.We reported the electron spin dynamics of dense Rb atoms which drastically depends on the polarization, the magnetic field, the atom density, and the pulse area of RF field. In the paper we demonstrated experimentally and theoretically the decay of atomic coherence is due to the spin-exchange interaction of dense Rb atoms.