Optische Spin-Polarisation im Triplett-Zustand von Naphthalin
Optische Spin-Polarisation im Triplett-Zustand von Naphthalin
复制标题
萘三重态光学自旋偏振
DOI：
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发表时间：
1969
期刊：
影响因子：
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通讯作者：
H. Slxl
中科院分区：
文献类型：
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作者：
M. Schwöhrer;H. Slxl
在非极化紫外激发下进入最低三重态的萘，在三个磁亚能级内与玻尔兹曼分布有明显的偏离。我们称这种偏差为光自旋极化。在混合晶体C10D8: 0.2% C10H8中，未氘化的naphthaln在4.2°K时起陷阱作用，光自旋极化超过热自旋极化，导致两个磁亚能级之间出现稳态反转。这导致了一个发射esr跃迁（微波的受激发射）。用两个不同速率常数的指数函数的叠加描述了紫外光打开或关闭后自旋极化的时间依赖性。—光自旋极化是由于系统间交叉过程（ISC）的自旋选择规则。这些主要涉及分子对称性。本论文的实验结果是抽运过程的选择规则：亚稳三重态是通过自旋分量τx填充的。三个自旋分量τx、τv和τz的消居率常数分别为kx = 0.65 sec-1、ky=0.4 sec-1和kz= 0。15秒1。自旋晶格弛豫概率是1秒-1的数量级。后者取决于磁场的方向和填充的三重态的浓度。这些结果与ISC理论进行了比较。
Naphthalene, which is excited into the lowest triplet state by unpolarized UV-Iight shows a strong deviation from the Boltzman distribution within the three magnetic sublevels, which is observed by ESR. We call this deviation optical spin polarization. In the mixed crystal C10D8: 0.2% C10H8 , where the undeuterated Naphthalene acts as trap at 4.2 °K, the optical spin polarization exceeds the thermal spin polarization such that a steady state inversion between two of the magnetic sublevels appears. This results in an emissive ESR-transition (stimulated emission of micro- waves). The time dependence of the spin polarization after switching on or off the UV-light is described by a superposition of two exponential functions with different rate constants. - The optical spin polarization is due to spin selection rules for the intersystem crossing process (ISC). These involve primarily the molecular symmetry. - The experimental results of the present paper are these selection rules for the pumping processes: The metastable triplet state is populated via the spin component τx.The depopulation rate constants of the three spin components τx, τv and τz are kx = 0.65 sec-1, ky=0.4 sec-1 and kz=O.15 sec-1 .The spin lattice relaxation probabilities are of the order of 1 sec-1. The latter are dependent on the direction of the magnetic field and on the concentration of the populated triplet states. - These results are compared with a theory of ISC.