Cross talk between experimental data and simple validation of shell closure in pre-actinides

TL;DR

This study investigates how shell closures in pre-actinides influence neutron multiplicity, validating the role of proton and neutron shell effects through experiments and data analysis, revealing a systematic increase in neutron multiplicity with increasing proton number.

Contribution

It provides new experimental validation of the influence of proton and neutron shell closures on neutron multiplicity in pre-actinides, linking proton and neutron shell effects systematically.

Findings

Neutron multiplicity increases with proton number from Z=82 to Z=88.

Cross-correlation shows systematic increase in Mtotal away from Z=82 and N=126.

Validation of shell closure effects through experimental data and comparison with previous results.

Abstract

Two back-to-back experiments, 28Si + 178Hf and 28Si + 186W, were intentionally conducted to validate the role of shell closure in pre-actinides by studying neutron multiplicity in compound nucleus (CN) 206Rn and 214Ra. In the first experiment, Dubey et al. [Phys. Rev. C 112, L011602 (2025)], we established the influence of the neutron shell closure. In the present work, the CN 214Ra was deliberately selected to investigate the dependence of the total neutron multiplicity (Mtotal) on the proton number (Z), while keeping the neutron number constant at N = 126 in the pre-actinide region. The objective of the study is two-fold : (i) to examine the effect of proton shell closure when moving away from Z = 82, and (ii) to correlate the present results on proton shell closure with our previous finding on neutron shell closure. We have also used the previous reported data for N = 126 isotones 210Po, 212Rn, and 213Fr to establish the validation of shell closure. A systematic increase in Mtotal with increasing Z was observed from Z = 82 to Z = 88. Furthermore, comparison of the present results on proton shell closure with our earlier neutron shell closure observation, reveals that the cross-correlation between neutron and proton shell closure shows a systematic increase in Mtotal as one moves away from 208Pb, whether along isotonic or isotopic chains.