Laboratory Measurements and Modeling of the Fe XVII X-Ray Spectrum
Laboratory Measurements and Modeling of the Fe XVII X-Ray Spectrum
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DOI：
10.1086/305941
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发表时间：
1998-08
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影响因子：
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通讯作者：
G. V. Brown;P. Beiersdorfer;D. Liedahl;K. Widmann;S. M. Kahn
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文献类型：
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作者：
G. V. Brown;P. Beiersdorfer;D. Liedahl;K. Widmann;S. M. Kahn
给出了Fe XVII l -壳发射光谱9.8 ~ 17.5 Å的详细测量、谱线识别和建模计算。测量是在电子束离子阱上进行的，在精确控制的条件下，电子冲击激发之后的辐射级联是主要的线形成过程。除了从n = 3壳层发出的强跃迁外，我们还识别并准确地确定了从更高的壳层到n = 11的跃迁的波长，包括两个以前未发现的电四极跃迁。各种理论值，包括新的畸变波计算，与我们的测量结果进行了比较，这为测试光谱建模预测建立了确定的值。我们发现2p-3d1P1共振强度和2p-3d3D1杂交线的强度之比分别为3.04±0.12，分别位于15.01和15.26 Å。该值高于在太阳光谱中观测到的值，这支持了太阳值受共振散射影响的说法。然而，由于我们的值明显低于计算值，散射量可能在过去的分析中被高估了。在较高主量子数n的水平上产生的跃迁的测量强度比与目前畸变波计算的比较表明，在n = 6之前，两者的一致性很好。相对于15.01 Å共振线的通量，所有n≥5的2p-nd跃迁和所有n = 4和5的2s-np跃迁的总通量为0.13+ 0.04−0.03。
Detailed measurements, line identifications, and modeling calculations of the Fe XVII L-shell emission spectrum between 9.8 and 17.5 Å are presented. The measurements were carried out on an electron beam ion trap under precisely controlled conditions where electron-impact excitation followed by radiative cascades is the dominant line formation process. In addition to the strong transitions emanating from the n = 3 shell, we identify and accurately determine wavelengths for transitions from higher shells up to n = 11, including two electric quadrupole transitions that have not been previously identified. Various theoretical values, including new distorted wave calculations, are compared to our measurements, which establish definitive values for testing spectral modeling predictions. We find a value of 3.04 ± 0.12 for the ratio of the intensity of the 2p-3d1P1 resonance and of the 2p-3d3D1 intercombination line situated at 15.01 and 15.26 Å, respectively. This value is higher than the values observed in solar spectra, which supports claims that the solar value is affected by resonant scattering. However, because our value is significantly lower than calculated values, the amount of scattering has probably been overestimated in past analyses. Comparisons of the measured intensity ratios of the transitions originating in levels of higher principal quantum number n with present distorted wave calculations show good agreement up to n = 6. The combined flux of all 2p-nd transitions with n ≥ 5 and all 2s-np transitions with n = 4 and 5 relative to the flux of the 15.01 Å resonance line has been measured to be 0.13+ 0.04−0.03 .