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Register a new userQuasi-$gamma$ band in $^{text{114}}$Te
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The low-lying non-yrast states in $^{114}$Te have been investigated using the Indian National Gamma Array through the fusion-evaporation reaction $^{112}$Sn($^{4}$He, 2n) at a beam energy of 37 MeV. Eight new $gamma$-transitions have been placed in the level scheme to establish the quasi-$gamma$ band in this nucleus. Spin and parity of several excited states have been assigned from the present spectroscopy measurements. The comparison of experimental results on the observed bands with the Interacting Boson Model (IBM) and Triaxial Projected Shell Model (TPSM) confirming the existence of the quasi-$gamma$ band structure in the $^{114}$Te nucleus.
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The emission of neutrons and gamma rays by fission fragments reveal important information about the properties of fragments immediately following scission. The initial fragment properties, correlations between fragments, and emission competition give rise to correlations in neutron-gamma emission. Neutron-gamma correlations are important in nonproliferation applications because the characterization of fissionable samples relies on the identification of signatures in the measured radiation. Furthermore, recent theoretical and experimental advances have proposed to explain the mechanism of angular momentum generation in fission. In this paper, we present a novel analysis method of neutrons and gamma rays emitted by fission fragments that allows us to discern structure in the observed correlations. We have analyzed data collected on ce{^{252}Cf}(sf) at the Chi-Nu array at the Los Alamos Neutron Science Center. Through our analysis of the energy-differential neutron-gamma multiplicity covariance, we have observed enhanced neutron-gamma correlations, corresponding to rotational band gamma-ray transitions, at gamma-ray energies of $0.7$ and $1.2$ MeV. To shed light on the origin of this structure, we compare the experimental data with the predictions of three model calculations. The origin of the observed correlation structure is understood in terms of a positive spin-energy correlation in the generation of angular momentum in fission.
Several new bands have been identified in 130Ba, among which there is one with band-head spin 8+. Its properties are in agreement with the Fermi-aligned u h11/2^2 , 7/2+[523] otimes 9/2-[514] Nilsson configuration. This is the first observation of a two-quasiparticle t-band in the A=130 mass region. The t-band is fed by a dipole band involving two additional h11/2 protons. The odd-spin partners of the proton and neutron S-bands and the ground-state band at high spins are also newly identified. The observed bands are discussed using several theoretical models, which strongly suggest the coexistence of prolate and oblate shapes polarized by rotation aligned two-proton and two-neutron configurations, as well as prolate collective rotations around axes with different orientations. With the new results, 130Ba presents one of the best and most complete sets of collective excitations that a gamma-soft nucleus can manifest at medium and high spins, revealing a diversity of shapes and rotations for the nuclei in the A = 130 mass region.
Low lying states of $^{198}$Hg have been investigated via $^{197}$Au($^{7}$Li, $ alpha $2n$ gamma $)$ ^{198} $Hg reaction at E$ _{text{beam}} $ = 33 MeV and 38 MeV and the members of $ gamma $-vibrational band have been identified. Results are compared with the systematic of this mass region and found in agreement. Observed band structures have been interpreted using the theoretical framework of microscopic triaxial projected shell model (TPSM) approach and it is shown that TPSM results are in fair agreement with the observed energies.
New data on both total and differential cross sections of the production of $eta$ mesons in proton-deuteron fusion to ${}^3text{He},eta$ in the excess energy region $13.6;text{MeV}leq Q_eta leq 80.9;text{MeV}$ are presented. These data have been obtained with the WASA-at-COSY detector setup located at the Forschungszentrum Julich, using a proton beam at 15 different beam momenta between $p_p = 1.60;text{GeV}/c$ and $p_p = 1.74;text{GeV}/c$. While significant structure of the total cross section is observed in the energy region $20;text{MeV}lesssim Q_eta lesssim 60;text{MeV}$, a previously reported sharp variation around $Q_etaapprox 50;text{MeV}$ cannot be confirmed. Angular distributions show the typical forward-peaking that was reported elsewhere. For the first time, it is possible to study the development of these angular distributions with rising excess energy over a large interval.
The observed variation of the total cross section for the dp -> 3He eta reaction near threshold means that the magnitude of the s--wave amplitude falls very rapidly with the eta centre--of--mass momentum. It is shown here that recent measurements of the momentum dependence of the angular distribution imply a strong variation also in the phase of this amplitude. Such a behaviour is that expected from a quasi--bound or virtual eta-3He state. The interpretation can be investigated further through measurements of the deuteron or proton analysing powers and/or spin--correlations.
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