Hyperfine Induced Transitions as Diagnostics of Isotopic Composition and Densities of Low-Density Plasmas
Hyperfine Induced Transitions as Diagnostics of Isotopic Composition and Densities of Low-Density Plasmas
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DOI：
10.1086/305690
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发表时间：
1998-06
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影响因子：
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通讯作者：
T. Brage;P. Judge;Abdellatif Aboussaïd;M. Godefroid;P. Jönsson;A. Ynnerman;C. Froese Fischer;D. Le
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作者：
T. Brage;P. Judge;Abdellatif Aboussaïd;M. Godefroid;P. Jönsson;A. Ynnerman;C. Froese Fischer;D. Le
J = 0 → J' = 0 辐射跃迁通常被认为是通过双光子衰变所允许的，也可能是由具有非零核自旋的原子或离子中的超精细 (HPF) 相互作用引起的。我们计算 Be (n = 2) 和 Mg (n = 3) 等电子序列离子中 nsnp3PoJ → ns21SJ'=0 跃迁的新衰变率并回顾现有衰变率。 J = 0 → J' = 0 跃迁的 HPF 感应衰减率比竞争的双光子过程的衰减率大许多数量级，并且当存在时，通常比这些离子的磁性四极 (J = 2 → J' = 0) 跃迁的衰减率小 1 或 2 个数量级。几种 HPF 诱导的跃迁可能对 C、N、Na、Mg、Al、Si、K、Cr、Fe 和 Ni 离子的天体物理学感兴趣。我们强调那些对于从 UV 或 EUV 发射线数据确定同位素丰度比和/或电子密度可能具有特殊诊断价值的情况。我们以标度定律的形式呈现原子数据，这样，在给定同位素核自旋和磁矩的情况下，一个简单的表达式就可以估算出 HPF 引起的衰变率。我们根据这些新结果检查了一些 UV 和 EUV 太阳和星云数据，并提出了未来研究的可能应用。我们无法在我们检查的光谱中找到 HPF 诱导线存在的证据，但我们证明现有数据已接近提供有趣的上限。对于行星状星云 SMC N2，我们从克莱格获得的戈达德高分辨率摄谱仪数据得出 13C/12C 的上限为 0.1。使用各种对象中具有更高灵敏度的新数据可能会获得更严格的限制。
The J = 0 → J' = 0 radiative transitions, usually viewed as allowed through two-photon decay, may also be induced by the hyperfine (HPF) interaction in atoms or ions having a nonzero nuclear spin. We compute new and review existing decay rates for the nsnp3PoJ → ns21SJ'=0 transitions in ions of the Be (n = 2) and Mg (n = 3) isoelectronic sequences. The HPF induced decay rates for the J = 0 → J' = 0 transitions are many orders of magnitude larger than those for the competing two-photon processes, and when present are typically 1 or 2 orders of magnitude smaller than the decay rates of the magnetic quadrupole (J = 2 → J' = 0) transitions for these ions. Several HPF induced transitions are potentially of astrophysical interest in ions of C, N, Na, Mg, Al, Si, K, Cr, Fe, and Ni. We highlight those cases that may be of particular diagnostic value for determining isotopic abundance ratios and/or electron densities from UV or EUV emission-line data. We present our atomic data in the form of scaling laws so that, given the isotopic nuclear spin and magnetic moment, a simple expression yields estimates for HPF induced decay rates. We examine some UV and EUV solar and nebular data in light of these new results and suggest possible applications for future study. We could not find evidence for the existence of HPF induced lines in the spectra we examined, but we demonstrate that existing data have come close to providing interesting upper limits. For the planetary nebula SMC N2, we derive an upper limit of 0.1 for 13C/12C from Goddard High-Resolution Spectrograph data obtained by Clegg. It is likely that more stringent limits could be obtained using newer data with higher sensitivities in a variety of objects.