Pulsed-beam measurements in 86Y

A new short-lived isomeric state with T1/2 = 125(5) ns has been identified previously in the odd-odd 86Y nucleus and its g-factor has been measured. In this work new pulsed-beam measurements have been performed aiming to elucidate the isomeric state properties. The experiments have been performed at the U-120 Cyclotron in Bucharest. The 86Y nuclei were populated in the 86Sr(p,n) reaction with a 13.5 MeV proton pulsed beam on a target consisting of the 86SrCO3 chemical compound. The γ-ray angular distributions have been measured in-between the beam pulses by using HPGe detectors. The time-differential perturbed angular distributions (TDPAD) of delayed transitions have been measured using NaI(Tl) detectors positioned at the angles 0 angle and 90 angle with respect to the beam. The target has been placed in an external magnetic field of 32.0 kG. The spin-rotation patterns were obtained for the 94.3 and 208.3 keV transitions. Positive A2 coefficients have been determined for both transitions from angular distribution and TDPAD measurements. A pure E2 multipolarity has been assigned to the 94.3 keV isomeric transition. The M1 + E2 multipolarity with large mixing ratio δ(E2/M1)=1.07 assigned to the 208.3 keV transition has been confirmed by our data. On the basis of the obtained results Jπ 7- has been assigned to the isomeric state and its decay scheme is given. A value of gexp = -0.083(3) has been derived for the g-factor of the 7- isomeric state from the previous and present measurements, corresponding to a magnetic moment μexp = -0.581 (21) n.m. On the basis of the measured g-factor, the 7- isomeric state was interpreted by the πf5/2xνg9/2 configuration. The isomeric decay proceeds mainly via the 94.3 keV E2 transition to the 5- 208.3 keV state, with a strength of 10.6 W.u. what indicates a moderate collectivity. For the 84.2 keV E1 transition to the 8+ 218.5 keV isomeric state, which was described by the πg9/2xνg9/2 configuration, a strength of 3.2 x 10-7 W.u. has been determined. (authors)