The proton capture ([Formula: see text]) cross-sections for eight different atomic nuclei in the mass region [Formula: see text]–110 were calculated within the nuclear reaction model code TALYS. For all the reactions, we tested different combinations of inputs for level density (l.d) parameter and gamma strength function ([Formula: see text]). Finally, it was observed that the application of hybrid input in TALYS (macroscopic l.d and microscopic or semi-microscopic [Formula: see text] or in abbreviation mac-mic) resulted in successful agreement of theoretical prediction that the existing experimental data. Isospin correction was also incorporated in a few cases which improved the matching if the center-of-mass energy reached the threshold energy of the opening of ([Formula: see text]) channel. The corresponding thermonuclear reaction rates were calculated for all the nuclei and some discrepancies were found with the prediction of the NONSMOKER code. Using the particular mac-mic input combination, the cross-section and reaction rate for the nuclei [Formula: see text]Nb and [Formula: see text]Mo were calculated within TALYS. These two nuclei lack experimental data but are highly important for understanding early solar system processes. This is a rare attempt to explain the p-capture cross-section of different p-nuclei ([Formula: see text]–110 range) with similar set of input combinations in TALYS, which may help to remove the uncertainty generated due to the variation of input parameters within nuclear statistical model codes.

Temperature-dependent photon strength function (PSF) models, along with the widely accepted temperatureindependent Brink-Axel Lorentzian model, are investigated in their application to determine the properties of the giant dipole resonance (GDR) built on the excited states of nuclei up to a temperature approximate to 1.5 MeV. Three temperature-dependent models, namely, the simple modified Lorentzian model, the hybrid model by Goriely, and the generalized Lorentzian model of Kopecky and Uhl, are studied. The statistical model calculations with all PSF models reproduce the high-energy (E gamma approximate to 5-25 MeV) gamma -ray spectra originating from the decay of 62Zn and 201Tl compound nuclei reasonably well, and put forward approximately the same peak energy and strength of the GDR. Nevertheless, at a given temperature, significant variation is observed in the predicted GDR width, which may influence the theoretical models used to calculate the GDR width.

The radiative decay of the Hoyle state serves as the gateway to the production of heavier elements in a stellar environment. Here, we present an exclusive measurement of electric quadruple (E2) transitions of the Hoyle state to the ground state of 12C through the 12C(p, p′γγ)12C reaction. A triple coincidence measurement yields the radiative branching ratio Γrad/Γ = 4.01 (30) × 10−4. This result was corroborated by an independent experiment based on the complete kinematical measurement via 12C(p, p′)12C reaction, yielding a consistent result of Γrad/Γ = 4.04 (30) × 10−4. Combining our results with the currently adopted values of Γπ(E0)/Γ and Γπ(E0), the radiative width of the Hoyle state is determined to be 3.75 (40) × 10−3 eV. It is important to note that our finding do not align with a recently reported 34% increase in the radiative decay width of the Hoyle state but is consistent with the currently accepted value.

The high-energy gamma rays have been measured in proton and alpha-induced reactions on medium mass target nuclei In-11(5) and Sn-112, respectively. Theoretical analyses of the spectra have been performed within the Hauser-Feshbach statistical model and the Akkermans-Gruppelaar exciton model formalisms. It is observed that the proton-induced reaction has significant contribution from the direct-semidirect capture in the region E-gamma approximate to 10-20 MeV. The He-4-ion-induced reaction could be described reasonably well by the results of the statistical model calculations. A reduced level density parameter, as compared to that used for the proton-induced reaction, was required to explain the high-energy gamma-ray spectrum in the He-4-ion-induced reaction.

ABSTRACT We present the coefficient of viscosity ( ), entropy (S) and viscosity to entropy density (s) ratio ( ) for aqueous silver nanoparticle (AgNP) solution at temperatures T = 273–300 K performing experiments and examining the same with discrete dipole approximation (DDA) simulation. The experimental UV-Visible dipole extinction spectra of the nanoliquid, matched with simulations, explore cluster morphologies. The latter is used for the calculation of (cluster volume fraction ~ 4–10%; NP, cluster radii 8–15 nm and 35–55 nm, respectively). In addition, dimer (AgNP-AgNP) formation free energy and S are explored at those T’s. We determine ratio exploiting nanoparticle behaviour. The value of is found lower than that of water and similar to strongly correlated liquid He4, owing to higher S for NP agglomeration. Our results of , S and are also corroborated from hard sphere model calculation. This, to the best of our knowledge, is the first attempt to determine in NP.

Theoretical nuclear reaction codes are crucial for studying cross-section and S-factors of nuclear reactions required for the thermonuclear reaction rate calculations. We analyze two reactions 8Li([Formula: see text])11B and 14N([Formula: see text])15O, using both TALYS and EMPIRE codes. We stress that these reactions are highly important for CNO cycle but the extent of involvement of experimental datasets are meager and conflicting. For the first reaction, the trend of experimental data has been predicted satisfactorily by the codes. The reaction rate is also matched with REACLIB calculation. However, in 14N([Formula: see text])15O, none of the codes could predict the resonant structures in the experimental data at the lower energies. The importance of our work is a sincere attempt to validate the TALYS and EMPIRE predictions for cross-section, S-factor and the reaction rate, simultaneously.

The high-energy $\ensuremath{\gamma}$ rays have been measured in proton and $\ensuremath{\alpha}$-induced reactions on medium mass target nuclei $^{115}\mathrm{In}$ and $^{112}\mathrm{Sn}$, respectively. Theoretical analyses of the spectra have been performed within the Hauser-Feshbach statistical model and the Akkermans-Gruppelaar exciton model formalisms. It is observed that the proton-induced reaction has significant contribution from the direct-semidirect capture in the region ${E}_{\ensuremath{\gamma}} \ensuremath{\approx}10--20$ MeV. The $^{4}\mathrm{He}$-ion-induced reaction could be described reasonably well by the results of the statistical model calculations. A reduced level density parameter, as compared to that used for the proton-induced reaction, was required to explain the high-energy $\ensuremath{\gamma}$-ray spectrum in the $^{4}\mathrm{He}$-ion-induced reaction.

An experimental study on the temperature (T) dependence of giant dipole resonance (GDR) width was performed for the medium mass nucleus Kr-74 in the range of T approximate to 2-2.5 MeV at an average angular momentum of 26 (h) over bar using the O-16 + Ni-58 fusion reaction. The emitted high-energy gamma rays and evaporated neutrons were measured in coincidence with low-energy discrete gamma-ray multiplicities. The GDR parameters, nuclear level density parameter, and nuclear temperature were determined by the statistical model analysis of the high-energy gamma-ray spectra as well as evaporated neutron spectra. The measured GDR width is found to increase monotonically with temperature, in contradiction with the recent observation of the width saturation in Mo-88. Comparisons of the measured data with predictions of the adiabatic thermal shape fluctuation model and its refined version, the critical temperature included fluctuation model, are presented and discussed.

Evaluated experimental structure and decay data are presented for 12 known nuclides of mass 219 (Pb, Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa, U, Np). Recommended values are given for level parameters, γ and α radiations, and other spectroscopic information. No excited states are known in 219Bi, 219Po, 219Pa, 219U and 219Np. Except for isotopic identification, no information about its half-life or decay characteristics is available for 219Pb. For 219Po, several γ rays have been reported from the decay of 219Bi β− decay, but no level scheme has been proposed. For 219At, only four excited states are known from α decay of 223Fr. For 219Rn and 219Fr, only the low-spin states are known from α decays of 223Ra and 223Ac, respectively. For 219Ra, 219Ac and 219Th, mainly the data for high-spin states are available from in-beam γ-ray studies. For 219Ra, high-spin data are available from 2017He15, 1992Wi02 and 1987Co36, but evaluators find significant differences in relative photon branchings between the three studies. Detailed comments are given in the Adopted dataset for this nuclide. Half-lives of excited states are known only for seven levels in 219Rn, thus there is a general lack of knowledge about γ-ray transition probabilities. This work supersedes data in the previous evaluations of A=219 published by 2001Br31, 1992Br10 and 1977Ma30.

The collective rotational enhancement in the nuclear level density (NLD) arising due to nuclear deformation is still not well understood due to sparse experimental findings. To address this issue, angular momentum (J) gated neutron, proton and GDR γ-ray spectra have been measured from two deformed nuclei (169Tm and 185Re) and one near spherical nucleus (201Tl) by populating them around 26 MeV excitation energy. An enhanced yield compared to statistical decay is observed in all the three spectra (p, n, γ) for both the deformed nuclei but only statistical decay for near spherical nucleus. Intriguingly, the relative enhancement factors determined independently from all the spectra are very similar (≈10) for both the deformed nuclei. Moreover, the results indicate that the fadeout of the collective enhancement does not dependent strongly on the nuclear ground state deformation which is in stark contrast to the expectations of the phenomenological as well as microscopic calculations. The possible reasons for this discrepancy are discussed.

Metallic nanoparticle (NP) is one the most important nanostructures used in medical purposes. However, for successful use of NPs, the size, shape, and growth kinetics should be known. In this work, we have demonstrated how silver nanoparticle (AgNP) size and growth depend on silver nitrate (AgNO3) and sodium borohydride (NaBH4) concentrations. The morphology of clusters is simulated by validating the plasmon spectra, generated using DDSCAT (based on discrete dipole approximation) simulation, with the experimental UV–Visible (UV–Vis) spectra. We find that at the concentration [AgNO3] to [NaBH4] ratio of 10:1, the nanoparticle cluster size is smallest and spherical, while for the ratio 3.3:1 this is deformed and large. For the latter, we observe quadrupole plasmon resonance. The AgNP cluster size and growth are also investigated with elapsed time and the stability of the cluster is demonstrated with entropy estimation. Thus, this work could enlighten us to select the AgNP cluster size required for medical purposes by correctly choosing the concentrations of the chemical reagents. Finally, important sectors for future studies of AgNP using γ-radiation have also been discussed, which could be useful in cancer treatment.

The shear viscosity ($\ensuremath{\eta}$) of nuclear matter is investigated in different nuclei (nuclear mass $A\ensuremath{\approx}59--194$) using experimental giant dipole resonance (GDR) width ($\mathrm{\ensuremath{\Gamma}}$) at high angular momenta ($J=12--54$ $\ensuremath{\hbar}$) and temperatures ($T=1.2--2.1$ MeV) collected from the existing literature. $\ensuremath{\eta}$, calculated from $\mathrm{\ensuremath{\Gamma}}$, is found to increase with $T$ and $J$. We show that critical temperature included fluctuation model (CTFM) successfully describes $J$-induced $\ensuremath{\eta}$ even beyond critical angular momentum ${J}_{c}$ at different values of $T$. However, the Fermi liquid drop model (FLDM) could not explain the data at higher angular momenta. We propose the addition of a $J$-dependent term with the FLDM $\ensuremath{\eta}$ to improve the prediction at such high-$J$ region. The $\ensuremath{\eta}/s$ ratio, highly important for measuring fluidity, is calculated using $\ensuremath{\eta}$ and the entropy density $s$. The latter is estimated using the Fermi gas formula. Interestingly, the experimental value of the ratio is independent of $J$ and $A$ and comes within 2.6--6.0 $\ensuremath{\hbar}/4\ensuremath{\pi}{k}_{\mathrm{B}}$, which is very close to those of a partonic system like quark gluon plasma at high temperature.

Debasish Mondal,* Deepak Pandit, S. Mukhopadhyay, Surajit Pal, Balaram Dey, A. De, Srijit Bhattacharya, Pratap Roy, K. Banerjee, Soumik Bhattacharya, S. R. Banerjee. 1Variable Energy Cyclotron Centre, Kolkata 700064, INDIA 2Homi Bhabha National Institute,Training School Complex, Anushaktinagar, Mumbai-400094, INDIA 3Deptartment of Physics, Bankura University, Bankura – 722155, INDIA 4Department of Physics, Raniganj Girls’ College, Raniganj-713358, INDIA 5Department of Physics, Barasat Govt. College, Barasat, N 24 Pgs, Kolkata-700124, INDIA . * email: debasishm@vecc.gov.in

The evolution of the hot and rotating $^{43}\mathrm{Sc}$ nucleus to a highly deformed shape has been studied by measuring the high-energy $\ensuremath{\gamma}$ rays from the decay of the giant dipole resonance. The compound nucleus was populated at two initial excitation energies and average angular momenta of $\ensuremath{\approx}26$ and $31\ensuremath{\hbar}$ by using $^{16}\mathrm{O}$ beam of energies ${E}_{\mathrm{lab}}$ = 120 and 142 MeV, respectively. The evaporated neutron energy spectra have been measured for proper determination of nuclear level density. The angular momentum has been determined by measuring the low-energy $\ensuremath{\gamma}$-ray multiplicities. The high-energy $\ensuremath{\gamma}$-ray and neutron spectra were analyzed simultaneously. At $\ensuremath{\langle}J\ensuremath{\rangle}\ensuremath{\approx}26\ensuremath{\hbar}$ a near-oblate shape is observed, whereas at $\ensuremath{\langle}J\ensuremath{\rangle}\ensuremath{\approx}31\ensuremath{\hbar}$ a sharp peak is observed at ${E}_{\ensuremath{\gamma}}\ensuremath{\approx}10\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ pointing towards the transition to the Jacobi shape with quadruple deformation parameter $\ensuremath{\beta}\ensuremath{\approx}0.7$. The results have been corroborated by the theoretical calculations based on the rotating liquid drop model framework.

Following power law, Farr's law and IDEA model, we analyze the data of COVID-19 pandemic for India up to 2 May, 2020 and for Germany, France, Italy, the USA, Singapore, China and Denmark up to 26 April, 2020. The cumulative total number of infected persons as a function of elapsed time has been fitted with power law to find the scaling exponent (γ). The reduction in γ in different countries signals the reduction in the growth of infection, possibly, due to long-term Government intervention. The extent of infection and reproduction rate R_0 of the same are also examined using Farr's law and IDEA model. The new cases per day with time assume Gaussian bell shaped curve, obeying the rule that faster rise follows faster decay. In India and Singapore, the peak of the bell shaped curve is still elusive. It is found that, till date, countries such as Denmark and India implementing sooner lockdown have underwent lower number of new cases of infection. Daily variation shows, R_0 of all the countries is reducing, ushering in fresh hopes to combat COVID-19. Finally, we try to make a prediction as to the date on which the different countries will come down to daily cases of infection as low as one hundred (100).

AbstractThe corona virus (SARS-CoV-2) or Covid-19 pandemic is growing alarmingly throughout the whole world. Using the power law scaling we analyze the data of different countries and three states of India up to 1st April, 2020 and explain in terms of power law exponent. We find significant reduction in growth of infections in China and Denmark (γ reduced from approximately 2.18 to 0.05 and 11.41 to 6.95, respectively). Very slow reduction is also seen in Brazil and Germany (γ reduced from approximately 6 to 4 and 11 to 7, respectively). Infection in India is growing (γ=9.23) though lesser in number than that in the USA (highest γ of 16 approximately, studied so far), Italy and a few other countries. Among three Indian states the growth in West Bengal (γ=0.64) is much slower than other states like Maharashtra and Kerala (γ=3.23 and 3.32, respectively). Some future predictions, though not rigid, has also been incorporated in our analysis. The earlier lock-down and stricter measures from the Governments concerned are being thought to be the only possible solutions, in the present situation, to fight against this virus.

A. De, Deepak Pandit, Balaram Dey, Debasish Mondal, S. Mukhopadhyay, Surajit Pal, S.R. Banerjee and Srijit Bhattacharya Department of Physics, Raniganj Girls’ College, Raniganj-713358, India 2 Variable Energy Cyclotron Centre, Kolkata 700064, India 3 Department of Physics, Bankura University, Bankura, India (Ex)Variable Energy Cyclotron Centre, Kolkata 700064, India Department of Physics, Barasat Government College, Kolkata-700124, India . * email: srijit.bha@gmail.com

Nucleon-deuteron system, being the lightest few-body (three-nucleon) system, has for a long time been the testing ground for the study of few-body aspects of nuclear forces [1-6]. With the advent of time, there have been a large collection of high precision experimental data along with highly rich different theoretical approaches like those based on Faddeev theoretical calculations. Though the overall agreement between theory and experiment is rather good, there exist certain notable discrepancies, especially at and around the collinear region in the kinematically allowed phase space, where three-body force (3BF) effects are expected to be manifested [3,7] favourably. As a consequence of internal structure of nucleon, three-body force is likely to play an important role in the three-nucleon system. The existing discrepancies around the collinear region point to the necessity of including new ingredient like 3BF in addition to the standard two-body inputs in the 3N calculation. The present article aims at possible reduction/removal of the existing discrepancies [3-6] and to better understand the experimental distribution of three-body correlation cross sections in the proton induced break-up of deuterons at several incident energies and correlated pairs of angles, where notable discrepancies were found, at and around the kinematically predicted collinear regions.

We present an experimental investigation of thermal phase transition in atomic nuclei by measuring the gamma rays from the decay of the giant dipole resonance in Tm-169 populated by using the reaction He-4 Ho-165. The systematic measurement confirms the prolate shape, similar to the ground-state value, till temperature T = 1.23 MeV. Moreover, the present data, together with the previous experimental studies, point towards the persistence of prolate shape with deformation similar to that of the ground state till T = 1.5 MeV. In addition, the emergence and evolution of thermal fluctuations observed directly in the experiment suggest that the sharp phase transition from prolate to near spherical at T approximate to 1.7 MeV will not be evident experimentally due to statistical fluctuations owing to the finite size of the nucleus.

We present a probable experimental signature of collective enhancement in the nuclear level density (NLD) by measuring the neutron and the giant dipole resonance (GDR) $\gamma$ rays emitted from the rare earth $^{169}$Tm compound nucleus populated at 26.1 MeV excitation energy. An enhanced yield is observed in both neutron and $\gamma$ ray spectra corresponding to the same excitation energy in the daughter nuclei. The enhancement could only be reproduced by including a collective enhancement factor in the Fermi gas model of NLD to explain the neutron and GDR spectra simultaneously. The experimental results show that the relative enhancement factor is of the order of 10 and the fadeout occurs at $\sim$ 14 MeV excitation energy, much before the commonly accepted transition from deformed to spherical shape. We also explain how the collective enhancement contribution changes the inverse level density parameter ($k$) from 8 to 9.5 MeV observed recently in several deformed nuclei.