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

在这个项目中，我们打算另外使用同步辐射和磁共振成像来研究超极化稀有气体原子的激光光谱。高功率激光二极管的窄化将实现核自旋的有效偏振。我们认为，这种新的核极化方法是通过研究惰性气体原子与介质或磁性表面的相互作用而发展起来的。为了探测低场(10mT)核自旋的共振信号，我们研制了低频(10 kHz-10 MHz)磁共振装置。通过Rb原子的光泵浦，可以检测到气相Xe原子在1%处的偏振。通过去年发展起来的高功率半导体激光器，我们可以获得光子到Xe原子的高偏振度和角动量的有效转移。激光功率为2W，比之前报道的值弱10倍。今年我们利用广域激光列阵稳定激光频率，放大了窄带激光。该激光系统保证了生产超极化惰性气体的高效率。通过去除Rb原子，检测到了0.1%的偏振。对于纯Xe气体有可能获得更高的极化，因此我们需要找到Xe原子无损转移的条件，以便检测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、磁场、原子密度和射频场的脉冲面积。在本文中，我们从实验和理论上证明了原子相干性的衰减是由于密集的Rb原子的自旋交换相互作用造成的。

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.