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

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 $4f^{6}6s6p$ and $4f^{5}5d6s^{2}$ 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 [ $4f^{5}(^{6}$H0, 6F$^{0})$ $5d6s^{2 }+ 4f^{6}(^{7}$F) $6s6p(^{3}$P$^{0})$] have been interpreted with the help of our $\Delta T^{148, 154}$ values. 20 unassigned energy levels have been uniquely assigned to $4f^{5}5d6s^{2}$ configuration. The present study provides $\Delta T^{148, 154}$ values of the levels, which were tentatively assigned to $4f^{5}5d^{2}6s$ and $4f^{6}5d6p$ configurations. We could also identify $4f^{6}5d6p$ configuration for 12 unassigned levels