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首页> 外文期刊>New astronomy reviews >From collisional line broadening to atomic polarization and collisional depolarization; Astrophysical applications
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From collisional line broadening to atomic polarization and collisional depolarization; Astrophysical applications

机译：从碰撞线展宽到原子极化和碰撞去极化；天体物理应用

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As is well known, interpretation of spectral line shapes is essential for spectroscopic modeling in the laboratory and in astrophysics. Line broadening by collisions offers a tool for spectroscopic diagnostics of scalar physical quantities, especially densities of perturbers. Thanks to the growing accuracy and sensitivity of spectropolarimetric observations and to the progress of MHD modeling, interpretation of all the Stokes parameters of spectral lines nowadays becomes crucial and new tools leading to the determination of vectorial (or anisotropic) physical quantities have been created and are of increasing interest. In particular, interpretation of atomic polarization enables us to determine magnetic field vectors, velocity field vectors, and also to interpret anisotropic excitation of the atomic levels by collimated beams of energetic particles.rnAtomic polarization leads to a global polarization of the observed line. It is a consequence of a departure from LTE between the Zeeman sublevels, and is due to an anisotropic excitation of the atomic levels. This anisotropic excitation is often the result of the incident radiation field absorption. However, isotropic collisions between Zeeman sublevels try to restore LTE and to destroy this atomic polarization. So, a quantitative interpretation of these spectropolarimetric observations must take into account collisional depolarization (and also the possible polarization transfer between levels). In some cases, collisional depolarization can also be used for determining densities of perturbers.rnIn fact, collisional line broadening, atomic polarization and collisional theories are two complementary theories based on the same key approximations: "no back reaction" and "impact theory". For collisional widths and shifts, the pioneering work by Baranger created in the end of the fifties, was followed by many fruitful developements. For atomic polarization, the theory of the master equation, was created by Fano in the fifties and developed for polarization studies at the end of the sixties and seventies in the pioneering works by Cohen-Tannoudji and coworkers. It has also been extended by many fertile developments, in particular for astrophysics. The main features of the formalism of atomic polarization and colisional depolarization will be presented in parallel with collisional line broadening and astrophysical applications, especially for solar physics, will be reported.
机译：众所周知，光谱线形状的解释对于实验室和天体物理学中的光谱建模至关重要。碰撞引起的线展宽为光谱诊断标量物理量（特别是扰动密度）提供了一种工具。由于光谱极化观测的准确性和灵敏度不断提高，并且随着MHD建模的进展，如今对光谱线所有斯托克斯参数的解释变得至关重要，并且已经创建了确定矢量（或各向异性）物理量的新工具，并且这些新工具已经被广泛使用。越来越感兴趣。尤其是，原子极化的解释使我们能够确定磁场矢量，速度场矢量，并能够解释高能粒子准直光束对原子能级的各向异性激发。原子极化会导致观测线的整体极化。这是Zeeman子级之间偏离LTE的结果，并且归因于原子级的各向异性激发。这种各向异性的激发通常是入射辐射场吸收的结果。但是，塞曼子级之间的各向同性碰撞试图恢复LTE并破坏这种原子极化。因此，对这些光谱极化观测的定量解释必须考虑到碰撞去极化（以及层​​间可能的极化转移）。在某些情况下，碰撞去极化也可用于确定干扰物的密度。实际上，碰撞线展宽，原子极化和碰撞理论是基于相同关键近似值的两个互补理论：“无反反应”和“碰撞理论”。对于碰撞的宽度和位移，五十年代末期的Baranger进行了开创性的工作，随后进行了许多富有成果的发展。对于原子极化，主方程的理论是由法诺（Fano）在五十年代创立的，并在科恩·坦努吉（Cohen-Tannoudji）及其同事的开创性工作中于六十年代和七十年代末发展用于极化研究。许多可喜的发展也使它得到了扩展，特别是对于天体物理学。将与碰撞线展宽同时呈现原子极化和科氏消极极化形式主义的主要特征，并将报道天体物理学的应用，特别是对太阳物理学的应用。

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