Proton Polarization at Room Temperature wih Laser and it's application

我们在高于77开尔文的温度下，用3 KGauss的染料激光在掺并五苯的萘分子晶体中极化了质子。在这种新方法中，电子被激光束激发到高单重态，其中自旋轨道相互作用导致从单重态到中间三重态的转变。总电子自旋z分量为+1、0、-1的最低三重态的Zeeman亚能级居数分别为12%、76%和12%。在三重态的寿命期间（约20微秒），微波照射和外场同时被扫过，通过积分固体效应将两个塞曼亚能级之间的电子居群差转移到质子极化上。三重态上的电子衰减到基态，在基态上质子自旋在很长一段时间内保持极化。用大功率脉冲染料激光（λ =590 ~ 605nm）对掺并五苯（0.01 mol%）的萘中的质子进行了极化实验，在液氮温度下极化率约为34%。该值对应的增强因子为8*10^4。质子在3KG和7G场下的弛豫时间分别约为1000分钟和160分钟。该方法适用于广泛的自旋物理领域。由于目标没有发热问题，也没有严重的辐射损伤问题，因此可以用于强子和电子的高强度光束。其次，由于保持极化所需的磁场极低，靶材对极低动量带电粒子的实验是有用的。

We have polarized protons in molecular crystals of naphthalene doped with pentacene using a dye laser in 3 KGauss at the temperature higher than 77 Kelvin. In this new method electrons are excited to high singlet states with the laser beam, where the spin-orbit interaction causes the transition from singlet states to intermediate triplet states. The populations of the Zeeman sublevels of the lowest triplet states with Z-components of the total electron spin+1,0, -1 are 12,76 and 12% respectively. During the lifetime of the triplet state (some 20 microsec) microwave irradiation occurs and the external field is swept simultaneously to transfer the population difference of electrons between two Zeeman sublevels to the proton polarization by means of the integrated solid effect. Electrons on the triplet states decay to the ground state, where the proton spin remains polarized for a long time.We have tried to polarize protons in naphthalene doped with pentacene (0.01 mol%) with a high-power pulsed dye-laser (lambda=590-605nm) and got about 34% polarization at liquid nitrogen temperature. The enhancement factor corresponding to this value is 8*10^4. The relaxation times of protons are about 1,000 and 160 minutes in hte field of 3KG and 7G respectively. The method is applicable to the wide fields of spin physics. Since the target has no heating problem and no serious problem of radiation damage, it can be used for high-intensity beams of hadrons and electrons. Secondly, the target is useful for experiments with very low-momentum charged particles, since the necessary magnetci field to keep the polatization is extremely low.