Experimental Verification of Theoretical Configuration Mixing in the Energy Levels of Er II Spectra via Isotope Shift Measurements Using a FTS

We report the first detailed investigation on isotope shift, Δσ 166, 170 measurements carried out in the spectrum of singly- ionized erbium (Er II/ Er +) recorded with a FTS. Isotope shift in 85 spectral lines were determined in the 350- 590 nm wavelength region. The source was accomplished of mixture of highly enriched isotopes of 166Er: 170Er in 7:10 ratio respectively and the detector was a photomultiplier tube. These investigations have contributed significantly to the understanding of the 92 known energy levels of Er +. Level isotope shift, ΔT 166, 170 values have been evaluated for 29 even- and 63 odd- parity energy levels for the first time. On the basis of the derived level isotope shifts the configuration mixing was estimated for altogether 92 involved levels and compared those with the theoretically predicted configuration mixings available in the literature and found that both the theoretical and experimental mixings have excellent agreement with each other.