Nuclear spin determination of^100mY by collinear laser spectroscopy of optically pumped ions

Abstract

The nuclear spin of the τ 1/2 = 0.94 s isomer in 100 Y has been determined by collinear laser spectroscopy of optically pumped yttrium fission fragments at the IGISOL facility, JYFL. The isotopes 96,98,99,100 Y were produced by proton induced fission of natural uranium, and studied on the 4d5s 3 D 2 (1045 cm −1) → 4d5p 3 P 1 (32124 cm −1) transition at 321.67 nm. Enhancement of the population of the metastable 3 D 2 level was achieved by optically pumping the ground state population via the 5s 2 1 S 0 → 4d5p 1 P 1 transition at 363.31 nm while the ions were stored in a linear Paul trap. This data, when combined with previous spectroscopic results, gives sufficient information for the nuclear spin of 100m Y to be determined unambiguously as I = 4. This spin assignment reveals that 100m Y has an unexpectedly large dynamic contribution to its quadrupole deformation.

Shape evolution in yttrium and niobium neutron-rich isotopes

“…Figures 11 and 12 show the corresponding results for niobium isotopes. Our results are compared with isotope shifts from laser spectroscopy experiments [30,33,36] in the case of δ r 2 c and with mass measurements from Refs. [31,62] in the case of S 2n .…”

“…13 we have compiled the measured isotope shifts δ r 2 c for Mo [32], Nb [33], Zr [26], Y [30,36], Sr [22], Rb [21], and Kr [23] isotopes. These data are shown with solid symbols and connected with continuous lines.…”

“…On the other hand, in laser spectroscopy experiments the focus is aimed at measuring nuclear spins, magnetic dipole moments, spectroscopic quadrupole moments, and mean-square charge radii from isotopic shifts. Considerable progress has been achieved in recent years (for a review, see [8] and references therein), and the mass region studied in this work has received special attention [13,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”

Isotope shifts from collinear laser spectroscopy of doubly charged yttrium isotopes

“…Such an approach was used to avoid J l = 0 → J u = 1 ground-state transitions in order to determine the nuclear spin of 100m Y [23] and in niobium isotopes [5], where in the latter case the ground-state line (used for optical pumping) was additionally too weak for efficient collinear laser spectroscopy. For manganese, the optical pumping scheme utilized a ground-state line too weak for spectroscopy (but nevertheless could be saturated in the cooler-buncher), providing access to a more favorable line in terms of spectroscopic efficiency and sensitivity to the nuclear electric quadrupole moment [18,33].…”

“…Later, values of F and M were calculated using the MCDF method for two different transitions in the Y + ion. These were the aforementioned 363.3-nm transition and also the 321.7-nm 4d5s 3 D 2 → 4d5p 3 P 1 transition, where selected isotopes have been remeasured, ostensibly to determine the nuclear spin of 100m Y [23]. The calculations performed yielded inconsistent values of δ r 2 , scattering to either side of the semiempirical estimate [22].…”