Magnetic field dependence of triplet-state ONP: theoretical analysis in terms of level anti-crossings
Magnetic field dependence of triplet-state ONP: theoretical analysis in terms of level anti-crossings
复制标题
三重态ONP的磁场依赖性：能级反交叉的理论分析
作者：
D. Sosnovsky;K. Ivanov
本文介绍了一种基于三重态能级反交叉（拉克）分析的光学核极化（ONP）的理论方法。在这里，我们认为ONP形成的分子晶体掺杂适当的客体分子和ONP产生的金刚石晶体中含有带负电荷的氮空位（NV-）中心。在这两种情况下，由光激发产生的三重态的电子自旋极化转移到原子核，产生ONP。极化转移是最有效的在拉克;出于这个原因，我们详细考虑交叉的电子-核能级和不同的微扰项（来自各向同性和各向异性的超精细耦合，零场分裂和样品取向）的作用，这把这些交叉到拉克和引起ONP。分析结果支持数值计算的ONP场依赖性。因此，概述的LAC分析是解释ONP磁场依赖性的有用方法。图形摘要
ABSTRACT A theoretical approach to Optical Nuclear Polarisation (ONP) is described, which is based on the analysis of Level Anti-Crossings (LACs) in triplet states. Here we consider ONP formed in molecular crystals doped with suitable guest molecules and ONP generated in diamond crystals containing negatively charged nitrogen-vacancy (NV–) centres. In both cases, electron spin polarisation of triplet states generated by light excitation is transferred to nuclei giving rise to ONP. Polarisation transfer is most efficient at LACs; for this reason, we consider in detail crossings of electron–nuclear energy levels and the role of different perturbation terms (coming from isotropic and anisotropic hyperfine coupling, zero-field splitting and sample orientation), which turn these crossings into LACs and give rise to ONP. Analytical results are supported by numerical calculations of the ONP field dependences. Thus, the outlined LAC analysis is a useful approach for interpreting the ONP magnetic field dependence. GRAPHICAL ABSTRACT