Hyperfine-dependent gf-values of Mn I Lines in the 1.49-1.80 ?m H Band

The three Mn i lines at 17325, 17339, and 17349Å are among the 25 strongest lines (log(gf ) > 0.5) in theH band. They are all heavily broadened due to hyperfine structure, and the profiles of these lines have so far notbeen understood. Earlier studies of these lines even suggested that they were blended. In this work, the profilesof these three infrared (IR) lines have been studied theoretically and compared to experimental spectra to assistin the complete understanding of the solar spectrum in the IR. It is shown that the structure of these lines cannotbe described in the conventional way using the diagonal A and B hyperfine interaction constants. The off-diagonalhyperfine interaction not only has a large impact on the energies of the hyperfine levels, but also introduces a largeintensity redistribution among the hyperfine lines, changing the line profiles dramatically. By performing large-scalecalculations of the diagonal and off-diagonal hyperfine interaction and the gf -values between the upper and lowerhyperfine levels and using a semi-empirical fitting procedure, we achieved agreement between our synthetic andexperimental spectra. Furthermore, we compare our results with observations of stellar spectra. The spectra ofthe Sun and the K1.5 III red giant star Arcturus were modeled in the relevant region, 1.73–1.74 μm, using ourtheoretically predicted gf -values and energies for each individual hyperfine line. Satisfactory fits were obtainedand clear improvements were found using our new data compared with the old available Mn i data. A completelist of energies and gf -values for all the 3d54s(7S)4d e6D – 3d54s(7S)4f w6F hyperfine lines are available assupporting material, whereas only the stronger lines are presented and discussed in detail in this paper