Direct Evidence of Washing out of Nuclear Shell Effects

TL;DR

This study provides direct experimental evidence that nuclear shell effects diminish around 40 MeV excitation energy, impacting super heavy element production and nuclear physics models.

Contribution

It offers the first direct measurement of the excitation energy at which nuclear shell effects wash out, supported by experimental data and theoretical calculations.

Findings

Nuclear shell effects wash out at approximately 40 MeV excitation energy.

Fission fragment mass distributions show disappearance of shell effects at this energy.

Second peak of the fission barrier vanishes near the same excitation energy.

Abstract

Constraining excitation energy at which nuclear shell effect washes out has important implications on the production of super heavy elements and many other fields of nuclear physics research. We report the fission fragment mass distribution in alpha induced reaction on an actinide target for wide excitation range in close energy interval and show direct evidence that nuclear shell effect washes out at excitation energy ~40 MeV. Calculation shows that second peak of the fission barrier also vanishes around similar excitation energy.