Description of nuclear photoexcitation by Lorentzian expressions for electric dipole photon strength function

TL;DR

This paper presents Lorentzian models for electric dipole photon strength functions to describe nuclear photoabsorption, compares models with experimental data, and proposes energy-dependent extensions valid at high gamma-ray energies.

Contribution

It introduces simple Lorentzian-based models with energy-dependent widths that approximate the energy-weighted sum rule for E1 transitions at high energies.

Findings

Models fit experimental data well for even-even nuclei.

Energy-dependent widths improve high-energy predictions.

Proposed models satisfy sum rules approximately.

Abstract

The description of photoabsorption cross-sections of cold nuclei by closed-form Lorentzian models of photon strength functions for photoexcitation by electric dipole gamma-rays is considered. Systematics of the GDR parameters are given and input parameters of different analytical models are discussed The experimental data are compared with theoretical calculations for even-even nuclei using criteria of minimum of both least-square value and root-mean-square deviation factor. Simple extensions of the models with energy-dependent widths to high gamma-ray energies $\gtrsim $ 30MeV which hold the energy-weighted sum rule for E1 gamma-transitions in good approximation are proposed and tested.