Second spectrum of Chromium (Cr II) Part I: New energy level reanalysis

Abstract

Using a linked-parametric technique of level-fitting calculations in a multiconfiguration basis, a parametric fine structure (fs) analysis for both even and odd parities of Cr II was achieved. For the first time the fs parameter, magnetic Landé g-factor and the percentage of leading eigenvector values for more than one thousand levels are determined and given for these two sets. This study has led us to confirm in the whole the well founded basis of NIST team works but inevitably also to exchange assignments of some levels classified in earlier lists of energy levels and to shift positions of some quartets like 4 F J for instance. Furthermore we take this opportunity to add our predicted doublet, quartet and sextet locations for missing experimental levels up to 124,000 cm −1 .

Second spectrum of chromium (Cr II), Part III: Radiative lifetimes and transition probabilities from highly excited 3d45s levels

“…The compositions of the eigenvectors obtained in the present work for these levels are displayed in Table 1. For odd-parity levels the compositions were already given in our previous paper [1]. When comparing our fitted data to the experimental oscillator strengths, a very satisfactory agreement is observed on the whole except for the lines whose wavelengths are: λ air = 2787.…”

“…These very encouraging results incite us to extend the present work to Cr II transitions involving 3d 4 4d, 3d 4 nf (n = 4, 5) and highly excited 3d 4 4p levels. Table 1. Eigenvalue components of even-parity Cr II levels of interest in this study, more detailed than in our previous paper [1]. Level: Configuration to which belongs the even-parity level involved in the studied transitions and the designation of this level in LS coupling.…”

“…Eigenvalue components of even-parity Cr II levels of interest in this study, more detailed than in our previous paper [1]. Table 2 Comparison between experimental and calculated oscillator strength values.…”

“…This paper is the third part of a detailed and systematic analysis of the Cr II spectrum. As a reminder, in the first part [1] we have studied the fine structure in order to obtain level eigenvector to transform into actual intermediate coupling the transition matrix beforehand obtained in pure LS coupling with help of Racah algebra while, in the second part [2], our efforts were mainly focused on radiative transitions depopulating lowlying 3d 4 4p levels. For Cr II the most recent compilation of energy levels is due to Sugar & Corliss [3], based on the analysis of Kiess [4] who succeeded in classifying 1843 lines linking 138 even-parity levels of 3d 5 , 3d 4 4s and 3d 3 4s 2 configurations to 139 3d 4 4p oddparity levels.…”

“…Sansonetti et al [6][7][8] reported in turn new observations of Cr II some years later, in the near-ultraviolet region 1140-3400 Å, and also up to the infrared region: 2850-37 900 Å, using 10.7 m normal incidence vacuum spectrograph and FT700 vacuum ultraviolet Fourier transform spectrometer. In our recent study of the fine structure in Cr II [1], we notably revised the assignments of some levels wrongly classified in earlier lists of energy levels. We also shifted the positions of some quartets like 3d 4 5d 4 F J for instance and we predicted the positions of still missing levels.…”