New even-parity high-lying levels of Sm I and measurement of isotope shifts by two-color resonance ionization mass spectrometry

•Twenty-one new even-parity levels of Sm I are identified in 33,136-33,960 cm−1 region.•Angular momenta of sixteen new levels are assigned uniquely.•Isotope shifts between 154Sm and 144Sm are measured for sixteen high-lying levels.

In this work, we investigate the even-parity high-lying levels of Sm I in the energy region 33136-33960 cm−1 by performing two-color three-photon resonance ionization spectroscopy in an atomic beam coupled to a time-of-flight mass spectrometer using two tunable pulsed dye lasers. We observe twenty-one new and confirm eight previously reported even-parity energy levels of Sm I in this spectral region. Absolute energies of these levels are determined with an accuracy of ±0.3 cm−1. Using electric dipole selection rule, total angular momentum (J-value) of the most newly observed levels is assigned uniquely. Further, employing two-color three-step resonance ionization mass spectrometry, we measure the isotope shift between 154Sm and 144Sm of sixteen high-lying levels with a moderate accuracy of ±30 mK.