Optical isotope shifts in the 4${\mathit{f}}^4$5d ${}_{}{}^6{}_{}{}^{}$${\mathit{K}}_{9/2}$–(23 537${)}_{9/2}^0$ transition (5702 Å) of Nd ii have been measured using collinear fast-beam-laser spectroscopy. [The level notation (23 537${)}_{9/2}^0$ includes the term value of the level, its parity, and total angular momentum.] From the measured optical isotope shifts, changes in mean-square nuclear charge radii δ〈${\mathit{r}}^2$〉 (${\mathrm{fm}}^2$) among the five even-even neodymium isotopes with mass numbers 142–150 have been deduced: (142,144), 0.283(9); (144,146), 0.257(8); (146,148), 0.284(9); and (148,150), 0.385(12). And configuration admixtures of the previously unclassified (23 537${)}_{9/2}^0$ level were quantitatively analyzed to be 4${\mathit{f}}^4$6p, 4${\mathit{f}}^3$5${\mathit{d}}^2$, and 4${\mathit{f}}^3$5d6s with mixing probabilities 15%, 84%, and 1%, respectively.

• Received 26 November 1990

DOI:https://doi.org/10.1103/PhysRevA.44.1843