Measurement of Giant Dipole Resonance width at low temperature: A new experimental perspective

TL;DR

This study measures the GDR width evolution at low temperatures in 119Sb, revealing discrepancies with existing models and suggesting the need for revised theoretical approaches.

Contribution

It provides new experimental data on GDR width at low temperatures, challenging the predictions of the thermal shape fluctuation model.

Findings

GDR width remains constant up to ~1 MeV temperature

Measured data disagree with the thermal shape fluctuation model

Indicates failure of the adiabatic assumption at low temperature

Abstract

The systematic evolution of the giant dipole resonance (GDR) width in the temperature region of 0.9 ~ 1.4 MeV has been measured experimentally for 119Sb using alpha induced fusion reaction and employing the LAMBDA high energy photon spectrometer. The temperatures have been precisely determined by simultaneously extracting the vital level density parameter from the neutron evaporation spectrum and the angular momentum from gamma multiplicity filter using a realistic approach. The systematic trend of the data seems to disagree with the thermal shape fluctuation model (TSFM). The model predicts the gradual increase of GDR width from its ground state value for T > 0 MeV whereas the measured GDR widths appear to remain constant at the ground state value till T ~ 1 MeV and increase thereafter indicating towards a failure of the adiabatic assumption of the model at low temperature.