原子和离子的基态排列：漫射介质中天体物理磁场的新诊断
Ground-state alignment of atoms and ions: New Diagnostics of Astrophysical Magnetic field in diffuse medium
摘要：
本文讨论了一种研究弥漫性天体物理介质（如星际和星系间气体/等离子体）中磁场的新技术。该技术基于原子和离子在其基态或亚稳态中的角动量排列。由于处于这种状态的原子的寿命很长，各向异性辐射诱导的排列对弱磁场（$1{\rm G}\gtrsim B\gtrsim0.1μ$ G）敏感。这种排列通过吸收光和发射光的偏振来显示。各种具有基态或亚稳态精细或超精细分裂的原子表现出对齐，并且在某些情况下产生的偏振度超过20%。我们表明，在吸收的情况下，极化方向是平行或垂直于磁场，而更复杂的依赖关系出现的情况下，发射的对齐原子。我们表明，相应的研究磁场可以进行光学和紫外偏振。这些研究的一个独特之处在于它们可以揭示磁场的3D方向。此外，我们指出，从地面水平的精细和超精细状态之间的过渡所产生的辐射的偏振可以提供另一个有前途的诊断磁场，包括早期宇宙中的磁场。我们列举了几个行星际、星周和星际磁场的例子，利用基态原子排列效应研究这些磁场是很有前途的。
英文摘要：
We discuss a new technique of studying magnetic fields in diffuse astrophysical media, e.g. interstellar and intergalactic gas/plasma. This technique is based on the angular momentum alignment of atoms and ions in their ground or metastable states. As the life-time of atoms in such states is long, the alignment induced by anisotropic radiation is susceptible to weak magnetic fields ($1{\rm G}\gtrsim B\gtrsim0.1μ$G). The alignment reveals itself in terms of the polarization of the absorbed and emitted light. A variety of atoms with fine or hyperfine splitting of the ground or metastable states exhibit the alignment and the resulting polarization degree in some cases exceeds 20%. We show that in the case of absorption the polarization direction is either parallel or perpendicular to magnetic field, while more complex dependencies emerge for the case of emission of aligned atoms. We show that the corresponding studies of magnetic fields can be performed with optical and UV polarimetry. A unique feature of these studies is that they can reveal the 3D orientation of magnetic field. In addition, we point out that the polarization of the radiation arising from the transitions between fine and hyperfine states of the ground level can provide yet another promising diagnostics of magnetic fields, including the magnetic fields in the Early Universe. We mention several cases of interplanetary, circumstellar and interstellar magnetic fields for which the studies of magnetic fields using ground state atomic alignment effect are promising.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
