Experimental Studies on Electronic Configuration Mixing for the Even-Parity Levels of Gd I Using Isotope Shifts Recorded in the Visible Region with FTS

Abstract

Electronic configuration (4f6s6p + 4f5d6s6p + 4f5d6p) mixing studies in the high even-parity energy levels of Gd I spectrum have been carried out on the basis of isotope shift (IS) Δσ156,160 data recorded in 49 spectral lines partially in the visible wavelength region on Fourier Transform Spectrometer (FTS) and the relevant spectral line IS data available in the literature. We employed “Sharing rule” to the experimentally observed level isotope shifts (LIS) of the even-parity levels for finding the percentage composition of each configuration being mixed. An FTS spectrum of Gd I in the region of 365–495 nm acquired employing the highly enriched Gd isotopes in liquid nitrogen cooled hollow cathode lamp (HCL) as a light source and photomultiplier tube as the detector. The studies of altogether 48 even-levels have revealed that amongst the 20 high even parity levels assigned previously to>95%4f5d6s6p configuration, 10 levels have agreed verywell whereas 7 have exhibited large contribution of 4f5d6s6p configuration compared to 4f5d6p configuration and 3 levels have equal contribution of 4f5d6s6p and 4f5d6p configurations. Out of 8 unassigned levels, 6 have dominant 4f5d6s6p configuration compared to 4f5d6p configuration and the remaining two have dominancy in 4f5d6p configuration.