The FERRUM project: Experimental lifetimes and transition probabilities from highly excited even 4d levels in Fe ii

TL;DR

This paper presents experimental measurements of lifetimes and transition probabilities for highly excited Fe ii levels, providing critical data for astrophysical spectroscopy and atomic calculations.

Contribution

It reports new lifetime and f-value measurements for specific Fe ii levels using advanced laser and spectroscopic techniques, enhancing atomic data accuracy.

Findings

Measured lifetimes of 6 Fe ii levels at 10.4 eV.

Determined f-values for 14 transitions from these levels.

Data aids in benchmarking atomic calculations for astrophysics.

Abstract

We report lifetime measurements of the 6 levels in the 3d6(5D)4d e6G term in Fe ii at an energy of 10.4 eV, and f -values for 14 transitions from the investigated levels. The lifetimes were measured using time-resolved laser-induced fluorescence on ions in a laser-produced plasma. The high excitation energy, and the fact that the levels have the same parity as the the low-lying states directly populated in the plasma, necessitated the use of a two-photon excitation scheme. The probability for this process is greatly enhanced by the presence of the 3d6(5D)4p z6F levels at roughly half the energy difference. The f -values are obtained by combining the experimental lifetimes with branching fractions derived using relative intensities from a hollow cathode discharge lamp recorded with a Fourier transform spectrometer. The data is important for benchmarking atomic calculations of astrophysically important quantities and useful for spectroscopy of hot stars.