ナトリウム様鉄イオンの天体物理モデルのためのベンチマークデータを提供（Physicists Provide Benchmark Data of Sodium-like Iron Ions for Astrophysical Modeling）

2025-06-24

2025-06-20 中国科学院（CAS）

Figure 1. Experimental DR rate coefficients (black filled symbols) for sodium-like Fe¹⁵⁺. (Image from IMP)

中国科学院近代物理研究所（IMP）と国内外の研究機関は、天体物理モデリングの基準となるデータとして、ナトリウム様鉄イオン（Fe15+）の電子再結合（DR）率係数を高精度で測定した。これは、宇宙プラズマのスペクトル解析に不可欠なデータであり、特にX線源における鉄イオンの放射特性解明に貢献する。研究は蘭州の重イオン研究施設（HIRFL）の冷却蓄積リングで行われ、電子・イオン合流ビーム法を用いた。測定データは0–40 eVのエネルギー範囲で最新理論と一致し、摂動理論に基づく3手法で確認された。また、温度依存の再結合率も導出され、天体観測データの解釈精度向上が期待される。

＜関連情報＞

ナトリウム様鉄イオンの誘電再結合の絶対速度係数：実験と理論 Absolute Rate Coefficients for Dielectronic Recombination of Sodium-like Iron Ions: Experiment and Theory

H. K. Huang, W. Q. Wen, Z. K. Huang, Y. Yuan, C. Y. Zhang, R. Si, S. J. Wu, C. Y. Chen, S. Fritzsche, S. Schippers,…
The Astrophysical Journal Supplement Series Published: 2025 June 2
DOI:10.3847/1538-4365/adcc25

Abstract

Absolute dielectronic recombination (DR) rate coefficients for sodium-like Fe¹⁵⁺ forming magnesium-like Fe¹⁴⁺ have been measured using the electron–ion merged-beams technique at the heavy ion storage ring Main Cooler Storage Ring, Lanzhou. The measured DR rate coefficients in the energy range from 0 to 90 eV cover all of the DR resonances due to 3s → 3p and 3s → 3d (Δn = 0) transitions and part of the DR resonances from 3s → 4ℓ (Δn = 1) core excitation. The experimental results are compared with theoretical calculations by using three independent state-of-the-art perturbative techniques: a multiconfiguration Breit–Pauli method using the AUTOSTRUCTURE code, a relativistic configuration interaction method using the Flexible Atomic Code and a multiconfiguration Dirac–Fock method using the Jena Atomic Calculator codes. Our theoretical results show excellent agreement with the experimental data in the energy range of 0–40 eV. However, in the energy range of 40–90 eV, a discrepancy is observed between the experiment and theory. Furthermore, temperature-dependent plasma recombination rate coefficients are derived from the measured DR rate coefficients over the temperature range of 10³–10⁸ K and are compared with previously available results in the literature. Within the temperature ranges relevant to photoionized plasmas and collisionally ionized plasmas, our results show good agreement with the experimental result from S. Schippers et al. (2010), as well as with the theoretical data of M. F. Gu (2004) and Z. Altun et al.; however, the earlier theoretical data from M. Arnaud & J. Raymond and P. Mazzotta et al., which are based on LS-coupling calculations, significantly underestimate the plasma rate coefficients in the low-temperature range. The present results provide a benchmark data set for astrophysical modeling.