Search

Employing the Argonne Fragment Mass Analyzer and the implantation-decay-decay correlation technique, a weak 0.50(21)% proton decay branch was identified in 108I for the first time. The 108I proton-decay width is consistent with a hindered l = 2 emission, suggesting a d 5 2 origin. Using the extracted 108I proton-decay Q value of 597(13) keV, and the Q α values of the 108I and 107Te isotopes, a proton-decay Q value of 510(20) keV for 104Sb was deduced. Similarly to the 112,113Cs proton-emitter pair, the Q p ( I 108 ) value is lower than that for the less-exotic neighbor 109I, possibly due to enhanced proton-neutron interactions in N ≈ Z nuclei. In contrast, the present Q p ( Sb 104 ) is higher than that of 105Sb, suggesting a weaker interaction energy. For the present Q p ( Sb 104 ) value, network calculations with the one-zone X-ray burst model Mazzocchi et al. (2007) [18] predict no significant branching into the Sn-Sb-Te cycle at 103Sn.

The second-phonon ( n ω = 2 ) wobbling band has been established in the nucleus 135Pr. Conclusive evidence for its wobbling nature comes from the Δ I = 1 , E2 character of the transitions between the new band and the previously identified transverse wobbler band ( n ω = 1 ) in this nucleus. Theoretical calculations in the framework of the quasiparticle triaxial rotor and triaxial projected shell models are found to be in good agreement with the experimental results.

Author(s): Salathe, M; Crawford, HL; Macchiavelli, AO; Kay, BP; Hoffman, CR; Ayangeakaa, AD; Campbell, CM; Clark, RM; Cromaz, M; Fallon, P; Jones, MD; Kuvin, SA; Sethi, J; Wiedeking, M; Winkelbauer, JR; Wuosmaa, AH | Abstract: The excitation energy of deformed intruder states (specifically the 2p2h bandhead) as a function of proton number Z along N=20 is of interest both in terms of better understanding the evolution of nuclear structure between spherical Ca40 and the Island of Inversion nuclei, and for benchmarking theoretical descriptions in this region. At the center of the N=20 Island of Inversion, the npnh (where n=2,4,6) neutron excitations across a diminished N=20 gap result in deformed and collective ground states, as observed in Mg32. In heavier isotones, npnh excitations do not dominate in the ground states but are present in the relatively low-lying level schemes. With the aim of identifying the expected 2p2h - s1/2+ state in P35, the only N=20 isotone for which the neutron 2p2h excitation bandhead has not yet been identified, the S36(d,He3)P35 reaction has been revisited in inverse kinematics with the HELical Orbit Spectrometer (HELIOS) at the Argonne Tandem Linac Accelerator System (ATLAS). While a candidate state has not been located, an upper limit for the transfer reaction cross section to populate such a configuration within a 2.5 to 3.6 MeV energy range provides a stringent constraint on the wave function compositions in both S36 and P35.

To forecast the plastic strain and flow behaviour of DP steel, a Bending under Tension (BUT) simulation and a micromechanical modelling based accession by aid of a Representative Volume Element (RVE) was engaged. The strain deformation behaviour is attained by applying macroscopic modelling of an orthodox Bending-Under-Tension (BUT) model. A consecutive microscopic modelling was enforced by acknowledging arbitrary phase distribution of close to practical microstructure by 2D RVE. Affinity amid microscopic behaviour and macroscopic (BUT model) comprising strain and stress distribution, were extracted from edge region RVE modelling. The macro-micro modelling prospective inflates the impression of steel microstructure, which will facilitate the microstructure to be implemented for numerous utilization in automobile industry.

High spin states of $^{37}\mathrm{Ar}$, populated through the $^{27}\mathrm{Al}(^{12}\mathrm{C},np)^{37}\mathrm{Ar}$ reaction with a 40 MeV $^{12}\mathrm{C}$ beam, were studied using the Indian National Gamma Array (INGA) facility. The existing level scheme has been extended up to 10.5 MeV by adding some new levels and transitions. The spins and parities of the new levels were assigned from ${R}_{\mathrm{DCO}}$, ${R}_{\mathrm{ADO}}$, and linear polarization measurements. The spins and parities of the existing levels also were modified or confirmed in the present experiment. The multipole mixing ratios ($\ensuremath{\delta}$) for most of the transitions were measured and compared with the earlier measurements wherever available. Large basis shell model calculations with different particle restrictions in $sd$ and $pf$ orbitals were performed to understand the microscopic origin of these levels. A simple two-level mixing calculation was also performed to extract the amount of multiparticle multihole configuration mixing for a few levels.

The High-spin states in 195Tl, populated through the 185,187Re(13C, xn) fusion evaporation reaction at the beam energy of 75 MeV, were studied using the Indian National Gamma Array (INGA). More than 50 new γ transitions have been placed in the proposed level scheme which is extended up to the excitation energy of ≈ 5.6 MeV and spin=22.5ħ. Two pairs of degenerate bands based on two different quasi-particle configurations have been identified in this nucleus indicating the first observation of such bands in an odd-A nucleus in A∼190 region and signify the first evidence of multiple chiral bands in a nucleus in this region. The total Routhian surface calculations predict triaxial shapes for both the configurations and thereby, support the experimental observation. The importance of multiple neutron holes in the i13/2 orbital and the stability of shapes for these two configurations have been discussed. Keywords: Nuclear Structure, γ-ray spectroscopy, Doubly degenerate bands, TRS calculation

The structure of 71Zn was investigated by one-neutron transfer and heavy-ion induced complex (deep-inelastic) reactions using the GRETINA-CHICO2 and the Gammasphere setups, respectively. The observed inversion between the 9/2+ and 1/2− states is explained in terms of the role of neutron pairing correlations. Non-collective sequences of levels were delineated above the 9/2+ isomeric state. These are interpreted as being associated with a modest oblate deformation in the framework of Monte-Carlo shell-model calculations carried out with the A3DA-m Hamiltonian in the p f g 9 / 2 d 5 / 2 valence space. Similarities with the structure of Ni 40 28 68 were observed and the shape-coexistence mechanism in the N = 40 region of neutron-rich nuclei is discussed in terms of the so-called Type-II shell evolution, with an emphasis on proton–neutron correlations between valence nucleons, especially those involving the shape-driving g 9 / 2 neutron orbital.

Lifetimes of excited states of the ground-state rotational band in the $^{136}\mathrm{Sm}$ nucleus have been measured up to ${I}^{\ensuremath{\pi}}={20}^{+}$ using the Doppler-shift attenuation method. The states were populated in the reaction $^{107}\mathrm{Ag}$($^{32}\mathrm{S}$, $1p2n$) at 145-MeV beam energy and the $\ensuremath{\gamma}$ rays emitted from the excited states were detected using the Indian National Gamma Array at the Tata Institute of Fundamental Research, Mumbai. The extracted transitional quadrupole moments indicate a reduction of collectivity with increasing spin after the band crossing. The results have been compared with the predictions of the cranked shell model as well as the triaxial projected shell-model calculations and indicate that the nucleus evolves from prolate $\ensuremath{\gamma}$-soft to a stable triaxially deformed shape after the first and the second crossing involving $\ensuremath{\pi}{h}_{11/2}^{2}$ and $\ensuremath{\pi}{h}_{11/2}^{2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}^{2}$ configurations, respectively.

The excited states of 169Tm have been studied via the 169Tm(32S,32S′)169Tm* reaction at the beam energy of 164MeV. The $\gamma$-rays were detected using the Indian National Gamma Array (INGA) setup, composed of 19 Compton-suppressed clover HPGe detectors. A new level scheme of 169Tm with 11 newly placed $ \gamma$-rays has been proposed. A band crossing in the $ \pi [541]1/2^{-}$ band and several interband E1 transitions between this and the $ \pi [411]1/2^{+}$ ground-state band have been observed for the first time in this nucleus. The role of the $N=98$ deformed shell gap has been discussed by comparing the band crossing parameters of the negative parity bands in Tm and other neighboring nuclei. The origin of the interband E1 transitions has been investigated in terms of coupling to octupole degrees of freedom. The shape evolution of the Tm isotopes around $ N=98$ have been studied in the projected and cranked shell model approaches, both of which predict a change in shape from an axial prolate to a triaxial one after band crossing in these nuclei. The new data and the calculations help to understand the unusual structural phenomena reported for the nuclei with $ N=98$.

Author(s): Elman, B; Gade, A; Janssens, RVF; Ayangeakaa, AD; Bazin, D; Belarge, J; Bender, PC; Brown, BA; Campbell, CM; Carpenter, MP; Crawford, HL; Crider, BP; Fallon, P; Forney, AM; Harker, J; Liddick, SN; Longfellow, B; Lunderberg, E; Prokop, CJ; Sethi, J; Taniuchi, R; Walters, WB; Weisshaar, D; Zhu, S | Abstract: The neutron-rich Ni isotopes have attracted attention in recent years because of the occurrence of shape or configuration coexistence. We report on the difference in population of excited final states in Ni70 following γ-ray tagged one-proton, one-neutron, and two-proton knockout from Cu71, Ni71, and Zn72 rare-isotope beams, respectively. Using variations observed in the relative transition intensities, signaling the changed population of specific final states in the different reactions, the role of neutron and proton configurations in excited states of Ni70 is probed schematically, with the goal of identifying those that carry, as leading configuration, proton excitations across the Z=28 shell closure. Such states are suggested in the literature to form a collective structure associated with prolate deformation. Adding to the body of knowledge for Ni70, 29 new transitions are reported, of which 15 are placed in its level scheme.

High-spin states in Zr89 were populated in the Se80(C13,4n) reaction, and γ-ray coincidences were measured using the Indian National Gamma Array. The level scheme of Zr89 has been extended up to spin I=49/2 with the observation of a new dipole band. Directional correlation and polarization asymmetries of the γ rays have been measured to determine spin and parity of the levels. Line shapes of several transitions have been analyzed to determine lifetimes of the levels. Possible configurations of the band have been discussed using the cranked Nilsson-Strutinsky model. The calculations suggest a triaxial shape of the nucleus at high spins, and the band may represent rotation of the nucleus about the longest axis.

The high-spin states in 86 Sr nucleus were populated using the 76 Ge( 13 C, 3n) reaction at a beam energy of 45 MeV. The γ – γ and γ – γ – γ coincidence measurements were used to establish the level scheme up to 10.9 MeV excitation energy and spin I π = 19 + . In our preliminary results reported earlier, a positive-parity dipole ( Δ I = 1 ) band based on the 6878-keV level having M1 γ -ray transitions was identified. In the present work, the γ -rays and their sequence have been established for this band. The band may have a magnetic rotational character. The spin-parity of the levels were assigned by measuring the Directional Correlations of the Oriented (DCO) nuclei and the polarization asymmetry. The polarization measurements were performed for the first time for the γ -ray transitions in this nucleus. The experimental band structures were compared with the shell-model calculations using two recent effective interactions, JUN45 and jj44b in the 1 p 3 / 2 , 0 f 5 / 2 , 1 p 1 / 2 , 0 g 9 / 2 model space. From the Tilted-Axis Cranking (TAC) calculations, the 4-qp π ( g 9 / 2 ) 2 ⊗ ν ( g 9 / 2 ) − 2 configuration is suggested for the lower-part of the ( Δ I = 1 ) band up to spin I π = 16 + and the 6-qp π [ ( g 9 / 2 ) 2 ( f 5 / 2 ) 1 ( p 1 / 2 ) 1 ] ⊗ ν ( g 9 / 2 ) − 2 configuration for the upper-part of the band.

The yrast and a few of the yrare negative-parity states in the 49V nucleus have been investigated employing the 27Al(28Si, α2p)49V reaction. Most of the levels and the deexciting γ rays, reported earlier in 49V, have been observed in this measurement using the Indian National Gamma Array (INGA) spectrometer. Mean lifetimes up to the band-terminating state have been extracted following Doppler Shift Attenuation Method (DSAM), and reduced transition probabilities have been deduced. Large Scale Shell Model (LSSM) calculations in the full fp shell employing various effective interactions with no restrictions imposed on the valence orbitals have been performed. The results that have been obtained from calculations are in fair agreement with the experimentally obtained values.

We report the first observation of the ^{108}Xe→^{104}Te→^{100}Sn α-decay chain. The α emitters, ^{108}Xe [E_{α}=4.4(2) MeV, T_{1/2}=58_{-23}^{+106} μs] and ^{104}Te [E_{α}=4.9(2) MeV, T_{1/2}

Excited states of $^{87}\mathrm{Zr}$, populated in the reaction $^{60}\mathrm{Ni}(^{31}\mathrm{P}$, $3pn$) at a beam energy of 112.5 MeV, have been studied. Experimental information on two negative-parity bands has been significantly upgraded with the addition of new $\ensuremath{\gamma}$ rays and levels. Small values of the reduced transition probability $B(E2$) and a general absence of a measurable Doppler shift in the transitions suggest that the states are weakly deformed. Several positive-parity levels have been grouped into two bands based on their observed properties. Spin parities have been proposed for a majority of the states belonging to the different bands. Lifetimes have been measured for the eight states belonging to the two positive-parity bands from Doppler shift attenuation data, including an upper limit for the highest energy state. The behavior of the deduced $B(M1$) and $B(E2$) values as a function of level spin supports the interpretation of one of these bands within the framework of the shears mechanism. A study of these reduced transition probabilities in the light of the semiclassical model of the shears mechanism, proposed by Macchiavelli and co-workers, confirms this interpretation. The effective gyromagnetic ratio and the interaction strength between the two blades of the shears have been estimated from this study.

This paper reports on an investigation on the level structure of the odd-mass $^{29}\mathrm{Al}$ nucleus populated via heavy-ion induced fusion evaporation reaction. Rotational sequences with fast magnetic dipole transitions have been identified. These sequences exhibit the essential characteristic features of magnetic-rotation-like behavior, which has been corroborated through lifetime measurements using the Doppler shift attenuation method. The sequences also show features exhibited by axially deformed nuclei. Thus, the level structure presents the possibility of existence of multifaceted excitation modes in $^{29}\mathrm{Al}$, which are believed to be the first of its kind observed in the $A\ensuremath{\approx}$ 30 region. Shell model calculations, carried out within the $sd$-model space, qualitatively reproduce the experimental observations.

The single-neutron configurations of several low-lying states in $^{22}\mathrm{F}$ have been determined from neutron-adding cross sections of a ($d,p$) reaction using a $^{21}\mathrm{F}$ radioactive beam in inverse kinematics. Final states in $^{22}\mathrm{F}$ consisting of a proton in the $\ensuremath{\pi}0{d}_{5/2}$ orbital coupled to a neutron in either the $\ensuremath{\nu}0{d}_{5/2}$, $\ensuremath{\nu}1{s}_{1/2}$, or $\ensuremath{\nu}0{d}_{3/2}$ orbitals were observed up to an excitation energy of $\ensuremath{\sim}5$ MeV. Spectroscopic factors and strengths were determined from the angular distribution of the cross sections using a distorted wave Born approximation method. The distribution of the $\ensuremath{\nu}0{d}_{5/2}$ and $\ensuremath{\nu}1{s}_{1/2}$ strength was well described by all USD effective shell model interactions, while only the more recent USDA/USDB interactions showed a marked improvement in describing the observed $\ensuremath{\nu}0{d}_{3/2}$ strength. Diagonal two-body matrix elements of the ${(0{d}_{5/2})}_{J=0--5}^{2}$ effective nucleon-nucleon interaction were extracted from the data and compared with previous determinations of the same matrix elements from particle-particle and hole-hole spectra, as well as the calculated results of the USDA interactions. No significant discrepancies were observed. Inspection of the monopole energies showed that an improved agreement between the different empirical matrix elements is found if a mass dependence is included.

A sequence of low-energy levels in _{32}^{78}Ge_{46} has been identified with spins and parity of 2^{+}, 3^{+}, 4^{+}, 5^{+}, and 6^{+}. Decays within this band proceed strictly through ΔJ=1 transitions, unlike similar sequences in neighboring Ge and Se nuclei. Above the 2^{+} level, members of this sequence do not decay into the ground-state band. Moreover, the energy staggering of this sequence has the phase that would be expected for a γ-rigid structure. The energies and branching ratios of many of the levels are described well by shell-model calculations. However, the calculated reduced transition probabilities for the ΔJ=2 in-band transitions imply that they should have been observed, in contradiction with the experiment. Within the calculations of Davydov, Filippov, and Rostovsky for rigid-triaxial rotors with γ=30°, there are sequences of higher-spin levels connected by strong ΔJ=1 transitions which decay in the same manner as those observed experimentally, yet are calculated at too high an excitation energy.

In massive stars, the $^{41}\mathrm{Ca}(n,\ensuremath{\alpha})^{38}\mathrm{Ar}$ and $^{41}\mathrm{K}(p,\ensuremath{\alpha})^{38}\mathrm{Ar}$ reactions have been identified as the key reactions governing the abundance of $^{41}\mathrm{Ca}$, which is considered as a potential chronometer for solar system formation. So far, due to experimental limitations, the $^{41}\mathrm{Ca}(n,\ensuremath{\alpha})^{38}\mathrm{Ar}$ reaction rate is solely based on statistical model calculations. In the present study, we have measured the time-inverse $^{38}\mathrm{Ar}(\ensuremath{\alpha},n)^{41}\mathrm{Ca}$ and $^{38}\mathrm{Ar}(\ensuremath{\alpha},p)^{41}\mathrm{K}$ reactions using an active target detector. The reactions were studied in inverse kinematics using a 133-MeV $^{38}\mathrm{Ar}$ beam and $^{4}\mathrm{He}$ as the active-gas target. Both excitation functions were measured simultaneously in the energy range of $6.8\ensuremath{\le}{E}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\le}9.3$ MeV. Using detailed balance the $^{41}\mathrm{Ca}(n,\ensuremath{\alpha})^{38}\mathrm{Ar}$ and $^{41}\mathrm{K}(p,\ensuremath{\alpha})^{38}\mathrm{Ar}$ reaction rates were determined, which suggested a 20% increase in the $^{41}\mathrm{Ca}$ yield from massive stars.

The structure of deformed neutron-rich nuclei in the rare-earth region is of significant interest for both the astrophysics and nuclear structure fields. At present, a complete explanation for the observed peak in the elemental abundances at $A\ensuremath{\sim}160$ eludes astrophysicists, and models depend on accurate quantities, such as masses, lifetimes, and branching ratios of deformed neutron-rich nuclei in this region. Unusual nuclear structure effects are also observed, such as the unexpectedly low energies of the first ${2}^{+}$ levels in some even-even nuclei at $N=98$. In order to address these issues, mass and $\ensuremath{\beta}$-decay spectroscopy measurements of the $^{160}{\mathrm{Eu}}_{97}$ and $^{162}{\mathrm{Eu}}_{99}$ nuclei were performed at the Californium Rare Isotope Breeder Upgrade radioactive beam facility at Argonne National Laboratory. Evidence for a gap in the single-particle neutron energies at $N=98$ and for large deformation (${\ensuremath{\beta}}_{2}\ensuremath{\sim}0.3$) is discussed in relation to the unusual phenomena observed at this neutron number.

A beam containing a substantial component of both the J^{π}=5^{+}, T_{1/2}=162 ns isomeric state of ^{18}F and its 1^{+}, 109.77-min ground state is utilized to study members of the ground-state rotational band in ^{19}F through the neutron transfer reaction (d,p) in inverse kinematics. The resulting spectroscopic strengths confirm the single-particle nature of the 13/2^{+} band-terminating state. The agreement between shell-model calculations using an interaction constructed within the sd shell, and our experimental results reinforces the idea of a single-particle-collective duality in the descriptions of the structure of atomic nuclei.

International audience; Carbon burning is a critical phase for nucleosynthesis in massive stars. The conditions for igniting this burning stage, and the subsequent isotope composition of the resulting ashes, depend strongly on the reaction rate for C12+C12 fusion at very low energies. Results for the cross sections for this reaction are influenced by various backgrounds encountered in measurements at such energies. In this paper, we report on a new measurement of C12+C12 fusion cross sections where these backgrounds have been minimized. It is found that the astrophysical S factor exhibits a maximum around Ecm=3.5–4.0 MeV, which leads to a reduction of the previously predicted astrophysical reaction rate.

The present Rapid Communication reports conclusive evidence for an antimagnetic rotational band in the odd-odd $^{142}\mathrm{Eu}$ nucleus. The parity of the states of a quadrupole sequence in this nucleus is identified firmly from polarization measurements using the Indian National Gamma Array, and lifetimes of some of the states in the same structure are measured using the Doppler-shift attenuation method. The decreasing trends of the deduced quadrupole transition strength $B(E2)$ with spin in the sequence along with the increasing ${J}^{(2)}/B(E2)$ values conclusively establish the origin of these states as arising from antimagnetic rotation. The results are well reproduced by numerical calculations within the framework of a semiclassical geometric model.

The existence of $^{26}\mathrm{Al}$ (${t}_{1/2}=7.17\ifmmode\times\else\texttimes\fi{}{10}^{5}\text{ }\text{ }\mathrm{yr}$) in the interstellar medium provides a direct confirmation of ongoing nucleosynthesis in the Galaxy. The presence of a low-lying ${0}^{+}$ isomer (${^{26}\mathrm{Al}}^{m}$), however, severely complicates the astrophysical calculations. We present for the first time a study of the ${^{26}\mathrm{Al}}^{m}(d,p)^{27}\mathrm{Al}$ reaction using an isomeric $^{26}\mathrm{Al}$ beam. The selectivity of this reaction allowed the study of $\ensuremath{\ell}=0$ transfers to $T=1/2$, and $T=3/2$ states in $^{27}\mathrm{Al}$. Mirror symmetry arguments were then used to constrain the ${^{26}\mathrm{Al}}^{m}(p,\ensuremath{\gamma})^{27}\mathrm{Si}$ reaction rate and provide an experimentally determined upper limit of the rate for the destruction of isomeric $^{26}\mathrm{Al}$ via radiative proton capture reactions, which is expected to dominate the destruction path of ${^{26}\mathrm{Al}}^{m}$ in asymptotic giant branch stars, classical novae, and core collapse supernovae.

High-spin states in the $^{188}\mathrm{Pt}$ nucleus have been investigated employing the $^{174}\mathrm{Yb}(^{18}\mathrm{O},4n)^{188}\mathrm{Pt}$ reaction. The level scheme has been significantly extended with the addition of several new $\ensuremath{\gamma}$ rays. The Indian National Gamma Array (INGA) spectrometer consisting of eighteen clover Ge detectors facilitated angular correlation and linear polarization measurements for spin-parity assignment of levels. The ${I}^{\ensuremath{\pi}}={5}^{\ensuremath{-}}$ semi-decoupled band has been investigated in detail, and the long-standing ambiguity regarding the correct ordering of associated $\ensuremath{\gamma}$ rays is now removed with the new observation of transitions linking the even-spin levels to the odd-spin ones. A weak, $\mathrm{\ensuremath{\Delta}}I=2$ sequence of $\ensuremath{\gamma}$ rays with alignment and moment of inertia similar to the yrast, even-spin, rotation-aligned neutron ${i}_{13/2}$ band has been newly observed. Cranking calculations suggest that this new odd-spin sequence arises from the excitation of a valence quasineutron to the next ${i}_{13/2}$ level.

The high-spin states in $^{133}\mathrm{Cs}$, populated using the reaction $^{130}\mathrm{Te}(^{7}\mathrm{Li},4n)$ with 45-MeV beam energy, have been extended up to an excitation energy of 5.265 MeV using the Indian National Gamma Array. The observed one- and three-quasiparticle bands in $^{133}\mathrm{Cs}$, built on the $\ensuremath{\pi}{h}_{11/2},\phantom{\rule{0.28em}{0ex}}\ensuremath{\pi}{g}_{7/2}$, $\ensuremath{\pi}{d}_{5/2}$; and ${(\ensuremath{\pi}{g}_{7/2}\ensuremath{\pi}{d}_{5/2})}^{1}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}^{\ensuremath{-}2}$ configurations, respectively, have similar structure as seen in the lighter odd-$A$ Cs isotopes. The experimental level scheme has been compared with the large-scale shell model calculation without truncation using the $jj55pna$ interaction, showing a good agreement for both positive- and negative-parity states.

International audience; The 12C+12C fusion reaction is one of the most important for nuclear astrophysics since it determines the carbon ignition in stellar environments. Two experiments which make use of the gamma-particle coincidence technique to measure the 12C+12C S-factors at deep sub barrier energies are discussed. Results are presented showing a decrease of the S-factor below Ec.m. = 3 MeV.

Excited states in the $^{101}\mathrm{Pd}$ nucleus were investigated through the $^{75}\mathrm{As}(^{31}\mathrm{P},2p3n)$ fusion-evaporation reaction at ${E}_{\mathrm{lab}}=125$ MeV by using the Indian National Gamma Array spectrometer equipped with 21 clover Ge detectors. The level scheme is considerably extended for medium spin values. New positive-parity band structures in $^{101}\mathrm{Pd}$ have been studied within the framework of the projected shell model and are found to undergo transition from single quasiparticle to high-$K$ three quasiparticle configuration after band crossing, i.e., from principal-axis rotation to tilted-axis rotation. The negative-parity band structures are discussed in the framework of the hybrid version of tilted-axis cranking shell model calculations. The observed alignment gain in the lowest excited $\ensuremath{\nu}{h}_{11/2}$ negative-parity band results from successive ${(\ensuremath{\nu}{g}_{7/2})}^{2}$ and ${(\ensuremath{\pi}{g}_{9/2})}^{2}$ pair alignments. The higher excited negative-parity bands are reproduced for the $\ensuremath{\nu}[{h}_{11/2}{({g}_{7/2}/{d}_{5/2})}^{2}]$ and ${(\ensuremath{\pi}{g}_{9/2})}^{\ensuremath{-}2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ configurations.

The high-spin nuclear structure of the odd-odd $^{66}\mathrm{Ga}$ nucleus was probed using heavy-ion induced fusion-evaporation reaction. The de-exciting $\ensuremath{\gamma}$ rays were detected by using the Indian National Gamma Array (INGA) consisting of high resolution Compton suppressed clover detectors. The level scheme of $^{66}\mathrm{Ga}$ was extended up to an excitation energy $({E}_{x})$ of $\ensuremath{\sim}10.6$ MeV with spin parity of ${21}^{(+)}$. Two new quadrupole bandlike structures, one positive and one negative parity, based on the states having spin parity of ${J}^{\ensuremath{\pi}}={11}^{+}$ and ${10}^{\ensuremath{-}}$, respectively, were found. The experimental energy levels are compared with calculations within the framework of shell model calculation using $jj44bpn$ effective interaction. The agreement between experiment and theory is good. The total Routhian surface calculations were performed to understand the shape of the $^{66}\mathrm{Ga}$ nucleus associated with the configurations $\ensuremath{\nu}({g}_{9/2}){}^{3}\phantom{\rule{0.16em}{0ex}}\ensuremath{\nu}({f}_{5/2}){}^{2}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({g}_{9/2}){}^{1}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({f}_{5/2}){}^{2}$ and $\ensuremath{\nu}({g}_{9/2}){}^{2}\phantom{\rule{0.16em}{0ex}}\ensuremath{\nu}({f}_{5/2}){}^{1}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({g}_{9/2}){}^{1}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({f}_{5/2}){}^{2}$ assigned to the positive and negative parity bands, respectively. In the frequency domain $\ensuremath{\omega}=0.20\text{--}0.30$ MeV, both the negative and positive parity quadrupole structures, favor prolate deformation whereas at $\ensuremath{\omega}=0.50$ MeV there is a sudden change to noncollective oblate shape in both the bands.

The positive-parity band of 106Ag has been extended up to I = 25 ¯h and the lifetimes of the high spin levels of this band have been measured. The deduced transition rates decrease with increasing spin until I = 21 ¯h. Beyond this spin, the observed transition rates are substantially small and remain nearly constant. This is a novelobservation for a shears band. The observed features have been described within the framework of the shears mechanism with a principle axis cranking calculation.

Excited states in odd-odd 66Cu were investigated in a reaction between a 136MeV 30Si beam and a 65Cu target with the Indian National Gamma Array. Six new transitions have been identified including four transitions feeding the 600ns \(6^{-}\) isomeric state from an investigation of prompt-prompt and prompt-delayed coincidence events. The results of the present work have extended the level structure of this nucleus up to \(I^{\pi}=(9^{-})\). In addition, new information on the set of \( \pi p_{3/2} \nu g_{9/2}\) multiplets in this nucleus have been added. Shell model calculations were performed within the \( fpg_{9/2}\) and \( f_{5/2}pg_{9/2}\) model spaces. The results of shell model calculations using the \( fpg_{9/2}\) model space have been observed to be in better agreement with experimental excitation energies up to the highest spin observed. The results of the present work highlight the necessity of \( f_{7/2}\) proton holes to describe the positive as well as negative parity states in 66Cu.

The high spin excited states of $^{169}\mathrm{Tm}$ have been studied via the $^{169}\mathrm{Tm}$($^{32}\mathrm{S}$, $^{32}\mathrm{S}^{\ensuremath{'}}$)$^{169}{\mathrm{Tm}}^{*}$ reaction at a beam energy of 164 MeV. The $\ensuremath{\gamma}$ rays were detected using an array of 19 Compton-suppressed clover HPGe detectors. The band based on the $[411]1/{2}^{+}$ Nilsson orbital has been extended to observe the band crossing for the first time in this nucleus. A sharp backbending, similar to $^{165}\mathrm{Tm}$, is observed in this nucleus which is in complete contrast with its immediate neighbor $^{167}\mathrm{Tm}$. The data were interpreted in the cranked shell model approach by calculating the total Routhian surfaces, crossing frequencies, and the interaction strengths for these nuclei which are in excellent agreement with the experimental data. It is suggested that the $N=98$ deformed shell gap has larger effect in determining the nature of alignment than its shape driving effect.

Two opposite parity dipole sequences (DB I and DB II) in 142Eu have been investigated using the Indian National Gamma Array (INGA), and heavy-ion induced fusion-evaporation reaction, 116Cd(31P, 5n) at ELab = 148 MeV. The Configurations of these bands are assigned on the basis of tilted axis cranking covariant density functional theory (TAC-CDFT) calculations. The measured B(M1) and B(E2) rates of the DB I and DB II, have been well reproduced within the shears mechanism with the principal axis cranking model (SPAC) calculations leading to the conclusion that these bands have been based on the shears mechanism. The large B(E1) transition rates between DB I and DB II indicate the existence of octupole correlation in 142Eu that has also been corroborated through microscopic multidimensionally-constrained covariant density functional theory (MDC-CDFT) calculations. Thus, the present investigation leads to the novel observation of the presence of octupole correlation between two shears band. Keywords: Lifetime measurement, Tilted axis rotation, Principal axis rotation, Octupole correlation, 142Eu

High-spin band structures of $^{200}\mathrm{Tl}$ have been studied by $\ensuremath{\gamma}$-ray spectroscopic methods using the $^{198}\mathrm{Pt}(^{7}\mathrm{Li},5n)^{200}\mathrm{Tl}$ reaction at 45 MeV of beam energy. The level scheme of $^{200}\mathrm{Tl}$ has been extended significantly and several new band structures have been established with the observation of 60 new transitions. The $\ensuremath{\pi}{h}_{9/2}\ensuremath{\bigotimes}\ensuremath{\nu}{i}_{13/2}$ oblate band has been extended beyond the particle alignment frequencies. The band structures and the other excited states have been compared with the neighboring odd-odd Tl isotopes. Total Routhian surface calculations have been performed to study the deformation and shape changes as a function of spin in this nucleus. These calculations could reproduce the particle alignment frequency and suggest that the neutron pair alignment in $\ensuremath{\nu}{i}_{13/2}$ orbital induces $\ensuremath{\gamma}$ softness in $^{200}\mathrm{Tl}$.

A fast-timing experiment was performed at the Argonne National Laboratory in December 2015 and January 2016, measuring decay radiation of fission products from a Cf-252 fission source. Details of the set-up, integration with Digital Gammasphere, and the data acquisition system are presented. The timing performance of the set-up, capable of measuring lifetimes from the nanosecond region down to tens of picoseconds, is discussed. First preliminary results from the fast-timing analysis of the fission fragment data are presented.

© 2016 Elsevier B.V. The γ-ray tracking array GRETINA was coupled to the S800 magnetic spectrometer for spectroscopy with fast beams of rare isotopes at the National Superconducting Cyclotron Laboratory on the campus of Michigan State University. We describe the technical details of this powerful setup and report on GRETINA's performance achieved with source and in-beam measurements. The γ-ray multiplicity encountered in experiments with fast beams is usually low, allowing for a simplified and efficient treatment of the data in the γ-ray analysis in terms of Doppler reconstruction and spectral quality. The results reported in this work were obtained from GRETINA consisting of 8 detector modules hosting four high-purity germanium crystals each. Currently, GRETINA consists of 10 detector modules.

Excited states of $^{133}$La have been investigated to search for the wobbling excitation mode in the low-spin regime. Wobbling bands with $n_\omega$ = 0 and 1 are identified along with the interconnecting $\Delta I$ = 1, $E2$ transitions, which are regarded as one of the characteristic features of the wobbling motion. An increase in wobbling frequency with spin implies longitudinal wobbling for $^{133}$La, in contrast with the case of transverse wobbling observed in $^{135}$Pr. This is the first observation of a longitudinal wobbling band in nuclei. The experimental observations are accounted for by calculations using the quasiparticle-triaxial-rotor (QTR) model, which attribute the appearance of longitudinal wobbling to the early alignment of a $\pi=+$ proton pair., Comment: 9 pages, 6 figures, 1 table

The negative parity non-yrast band of $^{106}\mathrm{Ag}$ has been studied to investigate the falling trend in magnetic dipole transition rates. In this context, the level lifetimes of the excited levels of this band have been measured using the Doppler shift attenuation method. The comparison of the experimental Routhian and the transition rates with the numerical results of the shears mechanism with the principal axis cranking calculation indicates that this band is generated due to the shears mechanism involving the three proton hole configuration.

A Geant4 simulation code for the Indian National Gamma Array (INGA) consisting of 24 Compton suppressed clover high purity germanium (HPGe) detectors has been developed. The calculated properties in the energy range that is of interest for nuclear γ-ray spectroscopy are spectral distributions for various standard radioactive sources, intrinsic peak efficiencies and peak-to-total (P/T) ratios in various configurations such as singles, add-back and Compton suppressed mode. The principle of operation of the detectors in add-back and Compton suppression mode have been reproduced in the simulation. The reliability of the calculation is checked by comparison with the experimental data for various γ-ray energies up to 5 MeV. The comparison between simulation results and experimental data demonstrate the need of incorporating the exact geometry of the clover detectors, Anti-Compton Shield and other surrounding materials in the array to explain the detector response to the γ-ray. Several experimental effects are also investigated. These include the geometrical correction to angular distribution, crosstalk probability and the impact of heavy metal collimators between the target and the array on the P/T ratio.

The low-lying states of 108Ag near the I π = 6+ isomer have been investigated with the 11B + 100Mo reaction at 39 MeV beam energy. We aim at understanding the structure of the states near the isomer and identifying possible isomer depletion paths. From the γ–γ and γ–γ–γ coincidence analysis, spectroscopy of the excited states near the isomer has been carried out to establish new transitions and modification of the previously known level scheme. The present work suggests a total of three possible transitions at energies below 500 keV from the isomer to higher excited levels, whose subsequent decay can branch to the ground state. The spins and parities of these states have been established with angular correlation and polarization measurements. The branching ratios and multipolarities of the associated γ-rays were used in the estimation of the integral cross section for induced isomer depletion via these states. The experimental data have been compared to the results of projected Hartree–Fock calculations to understand the configurations of the levels.