IC418中荧光和复合对发射线的激发
Excitation of emission lines by fluorescence and recombination in IC418
摘要：
我们比较计算的强度线的CII，NI，NII，OI和OII与已发表的深光谱调查的行星状星云IC 418。我们的计算使用自洽星云模型和中央恒星大气的合成光谱，考虑到线激发连续荧光和电子复合。我们发现，由于星云的低激发条件，s，p和大多数d态的NII光谱被荧光激发。许多CII和OII线具有显著量的荧光激发。双光子激发了f和g态的所有谱线以及大多数OII谱线。在中性电离边界的NI四重态和OI三重态偶极允许线被激发的荧光，而五重态OI线被激发的复合。电子激发产生OI的禁戒线，连续荧光增强NI的禁戒线强度。因此，低于莱曼极限的荧光激发的谱线提出了一种新的诊断方法来探索星云光解区域的内边界。
英文摘要：
We compare calculated intensities of lines of CII, NI, NII, OI and OII with a published deep spectroscopic survey of planetary nebula IC 418. Our calculations use a self-consistent nebular model and a synthetic spectrum of the central star atmosphere to take into account line excitation by continuum fluorescence and electron recombination. We found that the NII spectrum of s, p and most d states is excited by fluorescence due to the low excitation conditions of the nebula. Many CII and OII lines have significant amounts of excitation by fluorescence. Recombination excites all the lines from f and g states and most OII lines. In the neutral-ionized boundary the NI quartet and OI triplet dipole allowed lines are excited by fluorescence, while the quintet OI lines are excited by recombination. Electron excitation produces the forbidden optical lines of OI, and continuum fluorescence enhances the NI forbidden line intensities. Lines excited by fluorescence of light below the Lyman limit thus suggest a new diagnostic to explore the inner boundary of the photodissociation region of the nebula.
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