Isotope shift studies in UV lines of Sm I on FTS: level isotope shifts and configuration assignments of the energy levels of neutral samarium atom

Abstract

Isotope shifts $\Delta \sigma^{148,154}$ in 200 spectral lines of neutral samarium atom (Sm I) in the region of 355-455 nm (28160-21970 cm-1) have been measured using a Fourier Transform Spectrometer. Isotope shift data in 187 spectral lines of Sm I are being reported for the first time. Level isotope shifts, $\Delta T^{148,154}$ of 119 high odd- and 7 low even-parity energy levels have been evaluated using present isotope shift data combined with the earlier available data. These $\Delta T^{148,154}$ values have enabled us to check the assignments to 4f 66s6p and 4f 55d6s 2 configurations of the odd-parity levels made earlier on the basis of parametric calculations. For several levels, the reported compositions of the mixed configuration of type [4f 5(6H0, 6F0) 5d6s 2 + 4f 6(7F) 6s6p(3P0)] have been interpreted with the help of our $\Delta T^{148,154}$ values. 20 unassigned energy levels have been uniquely assigned to 4f 55d6s 2 configuration. The present study provides $\Delta T^{148,154}$ values of the levels, which were tentatively assigned to 4f 55d 26s and 4f 65d6p configurations. We could also identify 4f 65d6p configuration for 12 unassigned levels.