States In 92Zr Research Articles

Mixed Symmetry States in 92Zr and 94Mo Nuclei

Mixed-symmetry states of 92Zr and 94Mo isotopes are investigated with the use of the collective models, Interacting Boson Model-2 (IBM-2) and Quasiparticle Phonon Model (QPM). The energy spectra and electromagnetic transition rates for these isotopes are calculated. The results of IBM-2 and QPM are compared with available experimental data. We have obtained a satisfactory agreement, and IBM-2 gives a better description. In these isotopes, we observe a few states having a mixed symmetry such as 2+2, 2+3, 3+1, and 1+s. It is found that these isotopes have a vibrational shape corresponding to the U(5) symmetry.

Improved limits on double beta processes in 92Mo

New limits on double beta processes in 92Mo have been obtained using a 400 cm3 HPGe detector and an external source of high-purity natural molybdenum. At confidence level CL= 90% they are 1.9 · 1020 y for the (0v + 2v)β+EC transition to the ground state, 8.9 · 1020 y and 8.1 · 1020 y for the (0v + 2v)ECEC transitions to first excited 2 1 + and 0 1 + states in 92Zr, correspondingly.

Elastic and inelastic scattering of 16O by 92Zr at energies near the Coulomb barrier

Angular distributions for the elastic and inelastic scattering of 16O by 92Zr were measured at 56 MeV bombarding energy, as well as excitation functions at θ c.m. = 174.7° from 34 to 54 MeV in order to study the Coulomb-nuclear interference in the excitation of the 2 + 1, 2 + 2 and 3 − 1 states of 92Zr. Data were also obtained for the ( 16O, 15N) ground-state proton transfer. The elastic and inelastic results were analyzed using coupled-channels calculations. None of the inelastic data could be fitted satisfactorily using the standard collective model. The interference pattern in the angular distribution for the 2 + 1 excitation could be reproduced by introducing a strong nuclear reorientation coupling for this state, accompanied by a transition coupling much stronger than expected from the B(E2) for this excitation. The best fit to the 3 − 1 results was also obtained with a large reorientation term. The 2 + 2 data could be matched by using a more diffuse transition potential. The transfer angular distribution was reproduced very well in the DWBA. The overall behavior of the measured excitation functions indicates that one or more of the interaction parameters in the model must vary with the bombarding energy in order to accommodate the 2 + 1 interference minimum seen near 47 MeV. We deduce values of B(E2)↑ of about 0.09 and 0.04 e 2b 2 for excitation of the 2 + 1 and 2 + 2 states, respectively, and B(E3)↑≈0.11 e 2b 3 for the 3 − 1 state.

A study of the 91Zr(d, p) 92Zr reaction using vector-polarized deuterons

Differential cross sections and vector analyzing powers were measured for the 91Zr( d , d) 91Zr and 91Zr( d , p) 92Zr reactions at an incident deuteron energy of 12 MeV. Deuteron optical-model parameters were determined from an analysis of the elastic data. Comparison of the proton data to DWBA predictions showed that the DWBA does not quantitatively reproduce the measured analyzing powers, hence empirical analyzing power calibration curves were required to analyze the data. New spectroscopic information about the configurations of the excited states in 92Zr has been determined and is compared to the results of previous experiments as well as a shell-model calculation. The results of this experiment are in quantitative agreement with the predictions of the shell-model calculation for most of the transitions although some discrepancies do exist.

Elastic and inelastic scattering of 40 MeV polarized protons from 90Zr and 92Zr

Analyzing powers and cross sections have been measured for elastic and inelastic scattering of 40 MeV polarized protons from 90Zr and 92Zr. The analysis has been carried out in the DWBA within the framework of the macroscopic and microscopic models. Furthermore, the coupled-channels calculations using the vibrational model and the full Thomas form for the spin–orbit potential give a very good description for both the cross sections and the analyzing powers of the iow-lying2+, 3−, 5−, and 4+ states in 92Zr and the 2+ and 3− in 90Zr. The cross section and analyzing power for the first 2+ state in these nuclei were compared with previous results at 30 and 20.3 MeV, and from this comparison a certain energy dependence of the relative strength of the spin–orbit deformation to the central deformation could be observed. Microscopic model calculations with tensor and spin–orbit components included in the projectile–target real interaction and with an exact treatment of knock-on' exchange have been performed for the 2+ states in these nuclei. An attempt has also been made in order to include the imaginary component in the N–N interaction. For these calculations, rather good agreement was obtained especially for the 2+ state in 92Zr but poor agreement for 90Zr. Finally, valence plus core polarization calculations have also been done and showed a very good agreement between theory and experiment for those 2+ transitions.

Absence of proton weak coupling states in93Nb

The reactions93Nb(p, p)93Nb,93Nb(p, n)93Mo, and93Nb(p, p′) through isobaric analog resonances in94Mo have been used to study the structure of low-lying93Nb states, specifically the degree to which these states can be described as single protons coupled to the core states of92Zr. Excitation curves were obtained from 5.8 to 7.6 MeV incident proton energy, for eight states in93Nb. Results of this work are compared to results from Coulomb excitation studies,93Nb(n, n′γ),93Nb(d,p),92Zr(3He,d),94Mo(d,3He) and other related work.

Spin-parity assignments for the low-lying states in 96,97Tc via the neutron decay of 0+ and 2+ analogue states

Abstract Three low-lying excited states in each of the nuclei 91Nb, 95Tc, and 97Tc were observed to be strongly populated by the neutron decay of the 2+ resonances in the compound nuclei 92Nb, 96Tc and 98Tc. These resonances are the isospin analogues of the first 2+ states of 92Zr, 96Mo, and 98Mo, respectively. The neutron decay of the ground state analogue of 98Mo was also investigated. These decays of the analogue resonances were investigated via (p, n) reactions. The resonance energies (lab energy) and widths for the 2+ resonances are: 4.154 ±0.010 MeV and 33± 2 keV, 3.908 ±0.010 MeV and 32 ±2 keV, and 4.330 ±0.010 MeV and 34 ±2 keV for the compound nuclei 92Nb, 96Tc, and 98Tc, respectively. The energy and width for the 0+ resonance for 98Tc are 3.505 ±0.010 nMeV and 25 ±3 keV. The resonance yields to the individual states are compared to the expected yields based on the optical-model transmission coefficients. From these yields and the shapes of the off-resonance angular distributions, the following spin-parities are assigned: 3 2 − and 5 2 − for the 651 and 670 keV states of 95Tc, respectively, and 3 2 − and 5 2 − for the 575 and 662 keV states of 97Tc, respectively.