ATOMIC-LEVEL PSEUDO-DEGENERACY OF ATOMIC LEVELS GIVING TRANSITIONS INDUCED BY MAGNETIC FIELDS, OF IMPORTANCE FOR DETERMINING THE FIELD STRENGTHS IN THE SOLAR CORONA

作者：Li, Wenxian; Yang, Yang; Tu, Bingsheng; Xiao, Jun; Grumer, Jon; Brage, Tomas^*; Watanabe, Tetsuya; Hutton, Roger; Zou, Yaming

来源：Astrophysical Journal, 2016, 826(2): 219.

DOI：10.3847/0004-637X/826/2/219

• atomic processes
• magnetic fields
• Sun: corona
• techniques: spectroscopic
• UV radiation

We present a measured value for the degree of pseudo-degeneracy between two fine-structure levels in Fe9+ from line intensity ratios involving a transition induced by an external magnetic field. The extracted fine-structure energy difference between the 3p(4)3d D-4(5/2) and D-4(7/2) levels, where the latter is the upper state for the magnetic-field induced line, is needed in our recently proposed method to measure magnetic-field strengths in the solar corona. The intensity of the 3p(4)3d D-4(7/2) -> 3p(5) P-2(3/2) line at 257.262 angstrom is sensitive to the magnetic field external to the ion. This sensitivity is in turn strongly dependent on the energy separation in the pseudo-degeneracy through the mixing induced by the external magnetic field. Our measurement, which uses an Electron Beam Ion Trap with a known magnetic-field strength, indicates that this energy difference is 3.5 cm(-1). The high abundance of Fe9+ and the sensitivity of the line's transition probability to field strengths below 0.1 T opens up the possibility of diagnosing coronal magnetic fields. We propose a new method to measure the magnetic field in the solar corona, from similar intensity ratios in Fe9+. In addition, the proposed method to use the line ratio of the blended line 3p(4)3d D-4(7/2,5/2) -> 3p(5) P-2(3/2) with another line from Fe X as the density diagnostic should evaluate the effect of the magnetic-field-induced transition line.

• 出版日期2016-8-1
• 单位复旦大学