The FERRUM Project: Experimental oscillator strengths of the UV 8 multiplet and other UV transitions from the $\mathsf{y^6}$P levels of Fe II

Abstract

Abstract. We report on experimental branching fractions (BFs) for 19 transitions from the three 3d 5 ( 6 S)4s4p( 3 P) y 6 P levels in Fe II, measured in Fourier transform spectra of a Penning discharge lamp and a hollow cathode lamp. The transition wavelengths span the interval between 1600 and 2850 Å. Absolute oscillator strengths ( f -values) have been derived by combining the BFs with experimental radiative lifetimes recently reported in the literature. Theoretical f -values have been calculated using configuration interaction wavefunctions. The new experimental and theoretical f -values are compared with data available in the literature and in databases. The strongest lines measured belong to the UV 8 multiplet of Fe II, which has one ground state transition appearing as a prominent feature at 1608 Å in interstellar spectra. The line is accompanied by a satellite at 1611 Å due to a level mixing, which is discussed in the paper.

Transition frequency shifts with fine-structure-constant variation for Fe II: Breit and core-valence correlation corrections

“…These tables confirm assignment of the level 6 P o 7/2 at 62172 cm −1 to configuration 3d 5 4s4p. Moreover, the mixing of the configurations 3d 5 4s4p and 3d 6 4p for this level at a few percent was also independently confirmed from the analysis of the branching ratios [34]. Therefore, we conclude that application of the correction (3) is justified.…”

The FERRUM project: transition probabilities for forbidden lines in [Fe II] and experimental metastable lifetimes

“…Calculations are sensitive to level mixing and performing ab initio calculations which reproduce the mixing properties of the system is not trivial. This is illustrated in Nahar & Pradhan (1994), Nahar (1995), Hibbert & Corrégé (2005), Corrégé & Hibbert (2006) and Pickering et al (2002). In particular, Pickering et al (2002) emphasized that even though the agreement between the theoretical and experimental Fe ii Avalues investigated by Pickering et al (2002) are in general extremely good, probabilities related to spin forbidden transitions that occur due to level mixing may differ by up to an order of magnitude.…”

An Updated Constraint on Variations of the Fine-Structure Constant Using Wavelengths of Fe II Absorption Line Multiplets

“…In this study, we propose to make use of the Ritz wavelengths of 27 QSO absorption line spectra of Fe II to constrain any variations in the fine-structure constant on cosmological space and time scales [29][30][31][32][33]. Combining high precision measurements of the light from distant quasars together with laboratory wavelengths of the measured lines, this result is significantly tighter than the previously derived results using the MM method [34].…”

“…This method has a great benefit in that it allows us not only to apply it to the emission lines, but also to the absorption lines, as well as into wide ranges of redshifts. The spectra employed in this particular study are the same as those presented in References [29,32,33], and a detailed procedure of the analysis together with Ritz laboratory wavelengths are presented in the works of Nave and Sansoneti (2011) [30] and Nave (2012) [31]. The details of the experiments with a discussion arising in the literature about the validity of the analysis are available in the papers [27][28][29].…”