We report the discovery of a new atomic nucleus 188At, which is the heaviest proton-emitting isotope known to date. The new activity was observed through the 107Ag(84Sr, 3n)188At fusion-evaporation reaction using the focal-plane spectrometer of the gas-filled recoil separator in the Accelerator Laboratory of the University of Jyväskylä, Finland. To fully interpret the experimental data, we have expanded the non-adiabatic quasiparticle model to treat nuclei in the beyond-lead region. The description reproduced the measured decay rate and pointed towards emission from an extremely prolate-deformed state with a dominant s1/2 proton component in the wave function. The Thomas-Ehrman shift can be enhanced in low angular momentum states, but such effects have not been observed in heavy nuclei. The single-proton separation energy of 188At deviates from that extrapolated from the systematics, which can be interpreted as the first evidence of this effect in heavy nuclei.

Nuclear structure properties of proton rich nuclei at the limits of stability are an importance input for nuclear astrophysics models. The theoretical interpretation of the experimental decay data of these nuclei, makes possible the assignment of nuclear levels, and proton separation energies, crucial to understand how the rp process for the formation of the elements flows, and how it ends.

Two triaxial states of the proton-decaying nucleus 147Tm were studied via a comparison of experimental data to results obtained through nonadiabatic quasiparticle calculations. The experimental data were collected in a recoil-decay tagging study using the vacuum-mode recoil separator MARA coupled with the JUROGAM3 & gamma;-ray spectrometer. The previously proposed level scheme above the triaxial 11/2- (& pi;h11/2) ground state was confirmed, and the level structure was expanded to cover the states above the weakly populated proton-emitting 5/2+ (& pi;d5/2) isomeric state. It was found that the isomeric state is also triaxial, and possibly more deformed than the ground state.

We present a detailed theoretical investigation of proton emission from 140Ho within the nonadiabatic quasiparticle approach. The calculated proton emission half-life reproduces well the measured data. The importance of triaxiality and of the residual np interaction are studied. The ground state spin and parity of 139Dy (daughter) and 140Ho (parent) are ascertained unambiguously as 7/2+ and 3-, respectively, by analyzing the rotational energies, half-lives, and branching ratios.

Using the fusion-evaporation reaction ^{96}Ru(^{58}Ni,p4n)^{149}Lu and the MARA vacuum-mode recoil separator, a new proton-emitting isotope ^{149}Lu has been identified. The measured decay Q value of 1920(20) keV is the highest measured for a ground-state proton decay, and it naturally leads to the shortest directly measured half-life of 450_{-100}^{+170} ns for a ground-state proton emitter. The decay rate is consistent with l_{p}=5 emission, suggesting a dominant πh_{11/2} component for the wave function of the proton-emitting state. Through nonadiabatic quasiparticle calculations it was concluded that ^{149}Lu is the most oblate deformed proton emitter observed to date.

Axial symmetry breaking in Tm-144 is probed by examining its proton emission fine structure. The ground-state spin and parity in Tm-144 and daughter Er-143 are assigned unambiguously based on the corroboration of our calculations with the present data. We establish the first microscopic description of fine structure in odd-odd proton emitters, which is capable of resolving ambiguities present in the assignments of transitions in such nuclei.

Proton emitters play an important role in deciding the path of the astrophysical rapid proton capture (rp) process. The lifetime of these nuclei depends on several factors, like the deformation, angular momentum of the emitted proton, residual interaction between valence proton and neutron (especially in case of odd-odd nuclei) and so on. Therefore, it is worth to investigate the structure of proton emitters to understand the rp process path. However, due to lack of data in this exotic region, the theoretical models should be robust and the dependence on the free parameters should be minimal. In this direction, we have developed the first microscopic approach to study the triaxially deformed odd-odd proton emitters. The application of the developed approach to 108I, a recently observed proton emitter to investigate the end cycle of the rp process, is discussed.

Using the fusion-evaporation reaction ^{96}Ru(^{58}Ni,p4n)^{149}Lu and the MARA vacuum-mode recoil separator, a new proton-emitting isotope ^{149}Lu has been identified. The measured decay Q value of 1920(20) keV is the highest measured for a ground-state proton decay, and it naturally leads to the shortest directly measured half-life of 450_{-100}^{+170}  ns for a ground-state proton emitter. The decay rate is consistent with l_{p}=5 emission, suggesting a dominant πh_{11/2} component for the wave function of the proton-emitting state. Through nonadiabatic quasiparticle calculations it was concluded that ^{149}Lu is the most oblate deformed proton emitter observed to date.

We have interpreted the recent observation [K. Auranen et al., Phys. Lett. B 792, 187 (2019)] of proton emission from I-108. We find that. deformation is crucial to reproduce the experimental data, and have identified the decaying state as the 1(+) state. The effect of the residual np interaction is also discussed. With the present calculation, we establish the first microscopic description of a triaxial odd-odd proton emitter.

The nonadiabatic quasiparticle approach is applied to study chiral doublet bands in $^{128}\mathrm{Cs}, ^{130}\mathrm{Cs}$, and $^{130}\mathrm{La}$. The calculated energy spectra and electromagnetic transition probabilities reproduce quite well the experimental data. $^{130}\mathrm{Cs}$ turns out to be a better example for chiral symmetry breaking than $^{128}\mathrm{Cs}$, unlike it has been suggested in earlier studies. We present the first theoretical investigation of chiral geometry and its correlation with the single-particle configurations in $^{130}\mathrm{La}$ to understand the mode of chirality, i.e., static or vibrational.

A large wealth of data and a variety of models led to significant progress in understanding the spectra of deformed nuclei. However, a robust theoretical approach, which is less reliant on adjustable parameters is still elusive. Due to the scarcity of data, this drawback gets more pronounced while studying the exotic nuclei. With the motive to overcome this difficulty, we have developed the nonadiabatic quasiparticle approach for the description of rotational states in triaxial deformed odd-odd nuclei. The rotation-particle coupling is carried out utilizing an appropriate basis transformation such that the matrix elements of the odd-odd system can be written in terms of the rotor energies. This provides the advantage of studying the role of core more efficiently as compared to the conventional particle rotor model. The residual interaction between the valence proton and neutron is incorporated in two reliable ways, namely, the constant potential form and the zero-range interaction.

One of the enticing manifestations of broken symmetries in atomic nuclei is the chiral doublet bands. We investigate such bands in 136Pm and 138Pm, to understand the underlying geometries and their correlations with the single-particle configurations. We identify such correlations leading to vibrational or static nature of chirality. Chirality withstands higher spins in 136Pm, unlike 138Pm. Our present calculations for 138Pm, confirm the newly assigned spin and parity 9+ state as band-head of the yrast band, based on {πh11/2⊗νh11/2} configuration.

The observation, and the theoretical interpretation of the decay of proton rich nuclei at the proton drip line, are a probe to the nuclear structure at the extremes of stability, with strong implications to nuclear astrophysics models. Nuclear levels, and proton separation energies, can be assigned in these studies, establishing information that could not be obtained otherwise due to very short lifetimes of these nuclei.

Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Morales, A. I.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs; Pfützner, M.; Regan, P. H.; Rudolph, D.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; De Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R.P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C.L.; Corsi, A.; Denis Bacelar, A. M.; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; Klupp, S.

The neutron-rich isotopes Tl-211,Tl-213, beyond the N = 126 shell closure, have been studied for the first time in isomer gamma-ray decay, exploiting the fragmentation of a primary uranium beam at the Fragment Separator-Rare Isotopes Investigation at GSI setup. The observed isomeric states in Tl-211,Tl-213 show a deviation from the seniority-like scheme of Tl-209. The possible interpretation of the data is discussed on the basis of energy-level systematics and shell-model calculations.

We discuss recent results on decay of exotic proton rich nuclei at the proton drip line with Z < 50, that are of great importance for nuclear astrophysics models.

We study the structure and decay properties of triaxially deformed odd-A proton emitter (147,147)mTm with the modified particle-rotor model, which utilizes the microscopic nonadiabatic quasiparticle approach. In this approach the core spectrum is coupled with the particle states and hence the rotor properties are carried forward to the odd-A system. We demonstrate the merits of this approach by explaining the measured rotational bands in the triaxial proton emitters Ho-141 and (TM)-T-145,147. With our calculated spectra and half-lives for the proton emission, we confirm the ground state of Tm-147 to be 11/2(-) and predict the positive parity isomeric state to be 5/2(+).

The low-lying rotational bands of triaxially deformed nuclei Pr-137, Pm-137 and Eu-139 are studied with a modified particle-rotor model following the nonadiabatic quasiparticle approach. The matrix elements of the odd-A nucleus are obtained in terms of a coupling matrix and the rotational energies of the even-even core. The spectra of the cores Ce-136, Nd-136 and Sm-138 indicate a strong influence of triaxial deformation and vibrational degrees of freedom. These properties are appropriately carried forward to the calculations for the odd-A nucleus. We demonstrate that the ground and side bands of the odd-A nucleus and its core can be explained with the same set of deformation parameters (beta(2),gamma). We argue that this method could be useful in studying the low-lying states in exotic nuclei also.

We discuss the formulation of a nonadiabatic approach to study the rotational states in triaxially deformed odd-A nuclei. The rotation- particle coupling is treated microscopically by coupling the triaxial rotor states of the even-even core with the states of the valence particle in order to obtain the matrix elements of the odd-A system. We arrive at a nonadiabatic quasiparticle approach where the rotational states can have contributions from various quasiparticle states near the Fermi level. We bring out the advantages of this approach over the conventional particle rotor model with a fixed or variable moment of inertia. One clear evidence favoring our approach is the rotation alignment phenomenon which is demonstrated in the case of Pm-137. We discuss our results for Nd-136 and Pm-137, and justify that this approach is suitable also for studying nuclei away from stability.

Swati Modi1,∗ M. Patial, P. Arumugam, L. S. Ferreira, and E. Maglione Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667, India Centro de F́ısica e Engenharia de Materiais Avançados CeFEMA, and Departmento de F́ısica, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, P1049-001 Lisbon, Portugal and Dipartimento di Fisica e Astronomia “G. Galilei”, and Istituto Nazionale di Fisica Nucleare, Via Marzolo 8, I-35131 Padova, Italy