The structure of the unnatural parity bands in 49V, populated through the 48Ti(4He, 2np)49V reaction induced by a 48 MeV α beam, have been studied utilizing the Indian National Gamma Array (INGA) facility. The level scheme up to Jπ = 19/2+ have been confirmed using the results obtained from relative intensity, directional correlation, and linear polarization measurements. Lifetimes of six excited states have been measured using the Doppler shift attenuation method (DSAM). The experimental findings have been compared with the results obtained from shell model calculations.

The low-lying level structure of 80Se was investigated via the 76Ge(9Be,2p3n) reaction at Elab ≈ 31 MeV using a Compton-suppressed HPGe clover array, and level lifetimes were measured with the Doppler-shift attenuation method. Measured excitation energies and B(E2) transition strengths are reasonably well reproduced by Interacting Boson Approximation (IBA) calculations. The observed excitation-energy and transition-strength patterns associated with the σ=5 and σ=3 representations, together with candidate members of the σ=1 representation, exhibit pronounced O(6)-like collective behavior in this five-boson system. The combined experimental observables and finite-boson IBA calculations indicate a surprisingly good correspondence with O(6) expectations for these selected collective structures. At the same time, the presence of low-lying 02+ and 23+ states that are not consistently accommodated within the same classification, together with a finite B(E2;03+→21+) strength, demonstrates that the O(6) limit does not provide a complete description of the low-energy spectrum. We therefore interpret the present results as evidence for pronounced O(6)-like collective structures embedded within a more complex nuclear structure of 80Se.

The excitation scheme of the ^65Zn (Z = 30, N = 35) nucleus has been probed following its population in the ^63Cu(α,pn) reaction at E_beam = 30 MeV and using an array of Compton suppressed HPGe clovers as the detection system. This work has identified several new transitions of the nucleus and have modified the placements of some of the previously known ones. The multipolarities and the electric/ magnetic nature of the observed γ-ray rays have been measured, using the conventional methodologies. The spin-parity assignments for the levels have consequently been made; some of the spin-parities are new while others are either validation of the existing values or are modified results based on the present analysis. The experimental level scheme exhibits collective as well as single particle structures. The measured level energies have been compared with those calculated in the framework of the large basis shell model using a model space of p_3/2, f_5/2, p_1/2, g_9/2 orbitals and two different interactions. The collective excitations of the nucleus were probed through the properties of its band structures and through the calculations of the Total Routhian Surface (TRS) for the associated deformations/ shapes. The results of this study brings out the essential features of evolving structural characteristics and developing collectivity with increasing number of nucleons outside a doubly-magic core and with their occupancy of deformation driving high-j orbitals.

Low-and intermediate-spin negative-parity band structures have been investigated in the 82Kr nucleus using the fusion-evaporation reaction 76Ge (9Be, 3n) at ELab approximate to 31 MeV. Lifetimes of the states of interest in 82Kr have been measured using the Doppler shift attenuation method with the help of the Indian National Gamma Array, and the parity of the states has been confirmed from polarization measurements. The deduced B(M1) and B(E2) values from the lifetime measurements in comparison with the particle rotor model and the total Routhian surfaces calculations reveal that the bands DB1 and DB2 are based on the collective oblate and prolate deformed core, respectively. The enhanced electric dipole strengths, B(E1)s, and dipole moments, |D0|s, for the parity-changing transitions connecting the negative-parity bands DB1 and DB2 to the ground-state positive-parity band QB1 ensure the octupole correlation in 82Kr.

Nucleosynthesis reaction networks leading to p-nuclei involve a combination of different types of photodisintegration and capture reactions, as well as β^+ decays or electron captures. Photodisintegration reactions involving α particles present a particular interest as they serve as branching points of the reaction networks. The cross sections of these reactions depend crucially on the α-nucleus interaction. The α optical model potential (AOMP) is determined mostly by means of experimental differential elastic scattering distributions. Several previous studies have focused on the case of ^144Sm, an intriguing p-nucleus that is semi-magic with 82 neutrons. This work presents new experimental data on α elastic and inelastic scattering on ^148Sm, its closest stable isotope. Isotopic effects on the description of the AOMP are studied, as well as their consequences on the prediction of α-induced reaction cross sections at astrophysical energies. It is shown that the isotopic ratio for (α,γ) cross sections can be multiplied up to a factor of two when these effects are included.

The excitation scheme of the 69Ga (Z = 31, N = 38) nucleus has been studied following its population in the 59Co(13C, 2pn) reaction at Elab = 45, 50 MeV, using an array of Compton suppressed high-purity germanium (HPGe) clover detectors as the detection system. The existing level scheme has been considerably extended with identification of new gamma-ray transitions and their multipolarity assignments. The level energies have been calculated in the framework of the large basis shell model, and their overlap with experimental values is satisfactory, subject to the choice of the interaction. The band structures identified in the nucleus have been characterized with the moment of inertia and aligned angular momentum, and compared to those of similar structures in the neighboring isotopes. The shapes corresponding to these bands have been probed regarding their total Routhian surface (TRS), which exhibited varied deformation characteristics, such as prolate and gamma softness, associated with the individual sequences. Further, evidence of strong octupole correlation has been identified from an E3 transition between bands of opposite parities. The study comprehensively brings forth multiple aspects of single particle and collective characteristics in the level structure of 69Ga.

The two known low-lying long-lived states in 178Ta, J(x)=1+(T1/2=9.3 min) and J(x)=7-(T1/2=2.36 h) are populated through the 175Lu(a,n) reaction with two different irradiation times. The resulting y decay spectra have been analyzed with an aim to resolve the ambiguity in the ground state assignment of 178Ta. From the simultaneous decays of the two activities, their percentage populations are determined to be (66.2 +/- 3.0)% for the 1+ state and (33.8 +/- 0.9)% for the 7-state. The experimental results are compared with a) theoretical calculations using the phenomenological Two Quasiparticle Rotor Model and b) reaction modeling using TALYS. The consistency between experiment and both theoretical approaches provides evidence for the 1+ state to be the ground state while the 7-could be an excited level at similar to 20 keV in the 178Ta level scheme.

Evidence of triaxial deformation and wobbling mode of excitation has been experimentally identified for the proton h9/2 configuration in 185Au by identifying the predominant electric quadrupole (E2) character of the interlinking γ-ray transitions between the yrast and the yrare bands from their directional correlation of oriented states ratio and the linear polarization measurements. Transverse wobbling (TW) is suggested from the decreasing nature of the wobbling energy (Ewob) with spin. This wobbling band has been compared with that in its neighbors 183,187Au. Theoretical calculations, based on triaxial particle rotor model framework, are found to well reproduce the experimental observations. The low-spin increasing part of the transverse wobbling energy as a function of spin is also established for the first time in a πh9/2 configuration with the observation of an experimental data of Ewob in this part. This observation, together with the longitudinal wobbling reported in 187Au, identified 185Au as a transitional nucleus for an evolution from transverse to longitudinal wobbling in Au isotopes for the πh9/2 configuration. The prediction of inverse proportionality of Ewob with short-axis moment of inertia in case of transverse wobbling has also been confirmed.

The excited nuclear states of 125Te were populated in a fusion-evaporation reaction using a target of 124Sn and alpha beam at 31 and 35 MeV energies. All the gamma-gamma coincidences were recorded using the Indian National Gamma Array at VECC, India, and processed by a digital data acquisition system. A total of 92 new gamma rays were identified and placed within the level scheme. Six new structures, three of positive parity and three with negative parity, have been identified. Previously observed level scheme has been verified and extended up to approximate to 5.7 MeV. The results were interpreted in the framework of the particle rotor model and possible configurations were assigned to the structures.

The excited states of odd-A nucleus 55Mn have been investigated using alpha-induced fusion evaporation reaction to explore the shape driving effect of proton f7/2 orbital below Z = 28 shell gap. A deformed band structure, based on pi f7/2 configuration has been identified at lower excitation with firm spin-parity assignments of the levels. Band crossing has been identified for the first time in this nucleus through the observation of back bending in one of the signature partners. The properties of this band has been compared with the similar bands in the neighboring isotopes, 57,59Mn. The Total Routhian Surface calculations predict prolate shape for all the three Mn isotopes below the band crossing. However, a change in shape is predicted by these calculations at higher frequencies beyond the particle alignment. An unnatural parity state has also been identified in 55Mn which has been found to decay by E3 and E1 transitions. This observation indicates, for the first time, the presence of octupole correlation in this nucleus. It has been discussed in the light of the octupole correlation observed in its isobar 55V and other nearby odd-odd nuclei.

Two previously known bands in the excitation scheme of the 154 Tb nucleus have been investigated for the multipolarity and the electric/magnetic nature of the intra- and inter-band transitions. The excited states of the nucleus were populated in an alpha-beam induced reaction and the y-rays emitted therefrom were detected using an array of Compton suppressed HPGe clover detectors. The experimental findings are indicative of a shape evolution of the nucleus and development of strong triaxiality at higher spins. The multipolarities of the inter-band transitions brings forth the same. Total Routhian Surface (TRS) calculations and those in the framework of Triaxial Projected Shell Model (TPSM) have been carried out and the results corroborate the proposition on triaxiality.

Excited structures in 104 Mo were populated by β decays of the ground and isomeric states in the neutron-rich nucleus 104 Nb. The beams were produced by the CARIBU facility at Argonne National Laboratory, re-accelerated by the ATLAS accelerator and implanted on a moving-tape system in the middle of the GAMMASPHERE array. Separate decay schemes for the two β-decaying states in 104 Nb were constructed for the first time. The structure of the isomers are discussed in the framework of the deformed Nilsson model and systematics of known quasiparticle structures in neighboring nuclei.

The electromagnetic properties of low-lying states in 70Ge were investigated via multistep Coulomb excitation of a 70Ge beam impinging on a 208Pb target at the ATLAS facility of the Argonne National Laboratory. A total of 27 transitional elements and six diagonal matrix elements coupling 11 low-lying states were extracted from the measured cross sections. These were used to calculate reduced transition probabilities, spectroscopic quadrupole moments, and rotational invariant shape parameters, providing enhanced precision and expanding on previous studies. The experimental data were compared within several theoretical frameworks, including the generalized triaxial rotor model, configuration-interaction shell-model calculations, and computations within the combined frameworks of relativistic density functional theory and the five-dimensional collective Hamiltonian. The results demonstrate a good agreement with the experimental data and, in conjunction with calculations using a two-state mixing model, support significant triaxiality and strong mixing between the 0+ 1 and 0+ 2 states. This results in the magnitudes of their respective quadrupole deformations [/rms(0+1 ) = 0.228 (3), /rms(0+ 2 ) = 0.273 (1)] being more similar than previously observed. The implications of these results for understanding the complex shape coexistence phenomena, the role of triaxiality, and shape evolution along the Ge isotopic chain are discussed.

Single-particle and collective excitations in 116Sb are studied using the reaction 115In(alpha, 3n) 116Sb at abeam energy of 40 MeV and investigated using gamma -ray spectroscopic techniques. The existing level scheme is extended with the observation of several new transitions. The previously known band structures are extended to higher spins. Measurements of the directional correlation from oriented states (DCO) ratio and polarization asymmetry of the observed gamma rays are carried out to assign the spin-parities of the excited levels, populated in the present work. New band structures are interpreted as being due to the coupling of the valence particles with the 2p-2h intruder states of the Sn core. Further, the collective band structures are discussed on the basis of their rotational properties, total Routhian surface calculations, and the triaxial projected shell model approach.

The deformation properties of the low-lying states in 74Ge have been investigated using multistep Coulomb excitation. The measurements were carried out with the advanced gamma -ray tracking array, GRETINA, and the CHICO2 particle detector. A comprehensive set of E2 transition and diagonal matrix elements was deduced following an analysis with the semiclassical coupled-channels code GOSIA. The data were compared with results of calculations carried out within the framework of the generalized triaxial rotor model as well as with the configuration interaction shell model and the symmetric rotor model. Results from calculations with covariant density functional theory were used to construct a five-dimensional collective Hamiltonian for further comparisons with the data. Collectively, the calculations provide an accurate reproduction of the experimental matrix elements and further support an understanding in terms of the coexistence of two axially asymmetric shapes. This leads to an overall interpretation of the underlying structure of 74Ge requiring triaxiality, as is also the case in the neighboring even-mass Ge isotopes.

A Magnetic Rotational (MR) band in 57Fe nucleus has been newly identified and established from the decreasing behaviour of the experimental electric dipole transition probabilities, B(M1), determined from the measured lifetimes of the states. This becomes the first nucleus in the lighter mass (A<60) region in which, the B(M1) values of an MR band are measured. A single-particle configuration of πf7/2−2⊗ν(p3/2f5/2p1/2)3 has been assigned to this MR band. This configuration, which involves only the negative parity proton and neutron orbitals below and above the Z,N = 28 shell closures, respectively, is a unique one which was not identified before for an MR band. The range of observed angular momenta for this band is congruent with this configuration and the experimental data are found to be in agreement with the SPAC (Shears mechanism with Principal Axis Cranking) and semi-classical calculations. Shell model calculations with GXPF1A interaction reproduce the observed levels in 57Fe including the band head of the MR band. This validates the assigned configurations of this band.

Positive parity band structures in 82Kr were investigated using the reaction 76Ge(9Be, 3n) at ELab approximate to 31 MeV with the help of the Indian National Gamma Array. The predominant E2 component of the AI = 1 band interlinking transitions and the decreasing nature of wobbling energy with spin were observed for the bands TW1 and TW2, reflecting their transverse wobbling character. The absolute B(E2) transition strengths of the zeroth and first phonon wobbling bands as well as the signature partner band were extracted from the lifetime measurements. The extracted B(E2) values in comparison with the triaxial projected shell model calculations confirm similar deformation for the three bands, which is an important characteristic of wobbling modes. This is conclusive evidence of transverse wobbling motion in an even-even nucleus based on a two-neutron configuration and also an observation of wobbling motion in the A approximate to 80 mass region.

The yrast and nonyrast states of 126 Te were populated in a fusion -evaporation reaction using a target of 124 Sn and alpha beam at 31 MeV energy. All the gamma - gamma coincidences were recorded using the Indian National Gamma Array at the Variable Energy Cyclotron Centre, India, and processed by a digital data -acquisition system. The level scheme was enriched with the addition of 65 new transitions and the identification of five new structures. Spin and parity assignments were made and the subsequent results were interpreted in the framework of the nuclear shell model using the large-scale shell -model code ANTOINE .

A positive parity sequence of ΔI=2 γ transitions has been identified above Iπ=9/2+ state (Ex=2019 keV) in 115Sb through in-beam γ ray spectroscopic technique. Rotational features of this sequence are found similar to a low-K decoupled band. Observation of this newly identified low-K decoupled band, along with the earlier reported strongly coupled high-K band in this nucleus, provides the first experimental evidence for prolate-oblate shape coexistence associated with g9/2 proton-hole configuration around Z=50 shell closure. Experimental results are reproduced reasonably well in the frameworks of the projected shell model and the total Routhian surface calculations.