g Factor of the Zr99 ( 7/

Abstract

The gyromagnetic factor of the low-lying E = 251.96(9) keV isomeric state of the nucleus 99 Zr was measured using the Time Dependent Perturbed Angular Distribution technique. This level is assigned a spin and parity of J π = 7/2 + , with a half-life of T 1/2 = 336(5) ns. The isomer was produced and spin-aligned via the abrasion-fission of a 238 U primary beam at RIBF. A magnetic moment |µ| = 2.31( 14)µN was deduced showing that this isomer is not single-particle in nature. A comparison of the experimental values with Interacting Boson-Fermion Model IBFM-1 results shows that this state is strongly mixed with a main νd 5/2 composition. Furthermore it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.

Shape phase transitions in odd-A Zr isotopes

“…[14] has also underestimated the measured value of this transition strength by a factor of five. In the present calculation the B(E2) values for the negative-parity states in 99 Zr are also by a factor of five to six lower than the experimental ones [15]. Nevertheless, the majority of the B(M1) values, as well as the magnetic moments for the low-lying positiveparity states, both the sign and magnitude, are nicely reproduced.…”

“…) transition rate in 99 Zr is experimentally suggested to be rather weak [15], similar to the neighbouring isotope 97 Zr. The predicted E2 strength for this transition is a bit larger, but is in the same order of magnitude as the experimental one.…”

“…Unlike 97 Zr, several band structures have recently been experimentally identified in the nucleus 99 Zr [14,15,47]. Both the experimental and theoretical positive-parity energy spectra in Fig.…”

“…The neighbouring odd-A Zr nuclei have also been extensively studied in experiments. Only in the last couple of years several measurements of various spectroscopic properties in odd-A Zr have been reported, e.g., 97 Zr [13], and 99 Zr [14,15]. In contrast, much less theoretical research has been devoted to shape-phase transitions in odd-A Zr nuclei.…”

Magnetic moment of the 11/2− isomeric state in Mo99 and neutron spin g

“…In the case of 99 Zr, where one can see that a compromise value of the quenching factor of ≈ 0.5 provides an optimum description of all three known magnetic moments, it was checked that the M 1 transition rates were rather insensitive to the variation of GS and thus the conclusions of refs. [36,37] do not change. One should note the similarity (in magnitude and sign) of the IBFM description of the magnetic moments of five states in 113 Cd (graphs (n) to (r) in Fig.…”