Isotope shifts and hyperfine structure of the Fe I 372 nm resonance line

TL;DR

This paper presents precise measurements of isotope shifts and hyperfine structure of the 372 nm resonance line in Fe I across all stable isotopes, providing detailed atomic data relevant for spectroscopy and astrophysics.

Contribution

The study provides the first comprehensive measurement of isotope shifts and hyperfine constants for the Fe I 372 nm line, including all stable isotopes and the hyperfine structure of $^{57}$Fe.

Findings

Measured isotope shifts for all stable Fe isotopes.

Determined hyperfine structure of $^{57}$Fe with high precision.

Derived field and specific mass shift coefficients for the transition.

Abstract

We report measurements of the isotope shifts of the $3d^64s^2 a ^5D_4 - 3d^64s4p z ^5F_5^o$ Fe I resonance line at 372 nm between all four stable isotopes $^{54}$Fe, $^{56}$Fe, $^{57}$Fe, and $^{58}$Fe, as well as the complete hyperfine structure of that line for $^{57}$Fe, the only stable isotope having a non-zero nuclear spin. The field and specific mass shift coefficients of the transition have been derived from the data, as well as the experimental value for the hyperfine structure magnetic dipole coupling constant $A$ of the excited state of the transition in $^{57}$Fe: $A(3d^64s4p z ^5F_5^o) = 81.69(86)$ MHz. The measurements were done by means of Doppler-free laser saturated-absorption spectroscopy in a Fe-Ar hollow cathode using both natural and enriched iron samples. The measured isotope shifts and hyperfine constants are reported with uncertainties at the percent level.