Collinear laser–ion-beam spectroscopy has been used to measure the hyperfine structure (hfs) of nine metastable even-parity levels (E<15000 ${\mathrm{cm}}^{\mathrm{-}1}$) and nine odd-parity levels (EV32000 ${\mathrm{cm}}^{\mathrm{-}1}$) in ${}_{}{}^{147}{}_{}{}^{}$,149Sm ii. The mass resolution of 1 part in 350 eliminates spectral congestion due to overlapping lines from neighboring isotopes. The kinematic compression of the Doppler width is essential to obtain the necessary spectral resolution (approximately 20 MHz) to completely resolve hfs. An optical pumping scheme is used to differentiate the upper and lower levels of the observed transitions. The resulting magnetic dipole hfs constants, A, for the even-parity states arising from the 4$f^6$${(\mathrm{}}^7$F)5d configuration that are nominally more than pure 90% LS coupled have been analyzed in terms of Sandars-Beck effective-operator theory. The analysis shows that these levels actually contain substantial admixture of open-shell s electrons.

• Received 30 April 1987

DOI:https://doi.org/10.1103/PhysRevA.36.2148