Systematic study of the (n,2n) reaction cross section for 121Sb and 123Sb isotopes

The cross sections of the 121Sb(n,2n) 120Sbm and 123Sb(n,2n) 122Sb reactions were measured at 12.50, 15.79 and 18.87 MeV neutron energies relative to the standard 27Al(n,α) 24Na monitor reaction using neutron activation and offline γ-ray spectrometry technique. Irradiations of the samples were performed at the BARC-TIFR Pelletron Linac Facility, Mumbai, India. The quasi-monoenergetic neutron was generated via the 7Li(p,n) reaction. Statistical model calculations were performed by nuclear reaction codes TALYS (ver. 1.9) and EMPIRE (ver. 3.2.2) using various input parameters and nuclear level density models. The cross sections of the ground and the isomeric state as well as the isomeric cross section ratio were studied theoretically from reaction threshold to 26 MeV energies. The effect of pre-equilibrium emission is also discussed in detail using different theoretical models. The present measured cross section were discussed and compared with reported experimental data and evaluation data of the JEFF-3.3, ENDF/B-VIII.0, JENDL/AD-2017 and TENDL-2019 libraries. A detailed analysis of the uncertainties in the measured cross section data was performed using the covariance analysis method. Furthermore, a systematic study of the (n,2n) reaction cross section for 121Sb and 123Sb isotopes were also performed within 14-15 MeV neutron energies using various systematic formulae. This work helps to overcome discrepancies in Sb data and illustrate a better understanding of pre-equilibrium emission in (n,2n) reaction channel.

Statistical model calculations of 72,73Ge(n,p) and 72,74Ge(n,α) reactions on natural Ge

Systematic experimental and theoretical investigations of the 72,73Ge(n,p)72,73 Ga and 72,74Ge(n,α)69,71Znm reaction cross sections are presented in the energy range from thresh- old to about 17 MeV neutron energy. The above reaction cross sections were measured from 8.8 to 11.4 MeV by using the activation method, relative to the 27Al(n,α)24Na refer- ence reaction. The quasi-monoenergetic neutron beams were produced via the 2H(d,n)3He reaction at the 5 MV VdG Tandem T11/25 accelerator of NCSR “Demokritos”. Statisti- cal model calculations using the code EMPIRE-II (version 2.19) taking into consideration pre-equilibrium emission were performed on the data measured in this work as well as on data reported in literature.

Comparative study of four reactions at onset of pre-equilibrium emission

The study of the emitted particles, comparing pre-equilibrium and thermal components, is a useful tool to examine the nuclear structure of emitters. Possible clustering effects, which may change the expected decay chain probability, could be highlighted on the competition between different reaction mechanisms. The NUCL-EX collaboration (INFN, Italy) has carried out an extensive research campaign on pre-equilibrium emission of light charged particles from hot nuclei. In this framework, the reactions 16O+30Si, 18O+28Si, 19F+27Al at 7 AMeV and 16O+30Si at 8 AMeV have been carried out using the GARFIELD+RCo array at Legnaro National Laboratories. Some anomalies in the α-particle emission channels have been evidenced in the measurement reported above, showing in an exclusive way the observed effects related to the entrance channels. The experimental results are compared to model prediction, for which the same filtering and complete event selection have been applied.

Reaction mechanism of proton-induced pre-equilibrium α-particle emission from medium-mass nuclei at incident energies between 65 and 160MeV

The intrinsic reaction mechanism of proton-induced composite particle pre-equilibrium emission is well known to be a statistical multistep process. However, until recently it was still not clear how important the competition between pickup and knockout is to produce a composite ejectile in the multistep sequence. An evaluation of recent ([Formula: see text]) results at incident energies from 65 to 160[Formula: see text]MeV and on representative target nuclei is presented. The virtue of analyzing power angular distributions to unravel the details of the reaction mechanism is discussed and future possible avenues of investigation are explored.

Proton-induced pre-equilibrium composite-particle emission

The reaction mechanism of proton-induced composite particle pre-equilibrium emission as an intrinsic part a statistical multistep process was confirmed long ago. Nevertheless, until fairly recently it was still not clear how pickup and knockout processes compete in the multistep sequence to produce a composite ejectiles. An overview of results and conclusions based on recent (p,α) studies at incident energies from 65 to 200 MeV are presented and evaluated. It is shown how analyzing power is a valuable observable for unravelling the details of the reaction mechanism. Future avenues of investigation are discussed.