Distinctive features of Coulomb-related emissions in peripheral heavy ion collisions at Fermi energies

TL;DR

This paper investigates two distinct mechanisms of light charged particle emission in semi-peripheral heavy ion collisions at Fermi energies, highlighting differences in energy spectra and isotopic composition.

Contribution

It identifies and characterizes two separate emission processes, one evaporation-like and one midvelocity, in peripheral 93Nb+93Nb collisions at 38A MeV.

Findings

Evaporation process produces softer spectra and low N/Z ratio particles.

Midvelocity emission results in harder spectra with higher N/Z ratio.

Distinct kinetic and isotopic signatures differentiate the two mechanisms.

Abstract

Light charged particles emitted at about 90 deg in the frame of the projectile-like fragment in semi-peripheral collisions of 93Nb+93Nb at 38A MeV give evidence for the simultaneous occurrence of two different production mechanisms. This is demonstrated by differences in the kinetic energy spectra and in the isotopic composition of the particles. The emission with a softer kinetic energy spectrum and a low N/Z ratio for the hydrogen isotopes is attributed to an evaporation process. The harder emission, with a much higher N/Z ratio, can be attributed to a ``midvelocity'' process consisting of a non-isotropic emission, on a short time-scale, from the surface of the projectile-like fragment.