| Description |
Nuclear models representing the nature of ever-intriguing nuclear force can be robust if they render applicability over various domains, including the extremes of temperature (T), spin (I), isospin and density. Hence, extending the nuclear models to study nuclei at these extremes also gains significance, especially in the light of recent developments in the experimental facilities with which these nuclear states are becoming more accessible. Another important task in this regard is to identify the relevant phenomena for which the observables can be calculated reliably in all the considered domains. Giant resonance (GR) in nuclei is one such fundamental mode of excitation which can be built on any nuclear state. In a simplistic view, the GR are due to collective oscillations of protons and neutrons under the influence of the electromagnetic field induced by the emitted/absorbed photons, which results in a large peak in the emission/absorption spectrum of γ-rays. Among the various possible modes of the GR, the most dominant mode is the isovector giant dipole resonance which is commonly termed as GDR. Constructing a theoretical framework to study the GDR built on various nuclear states so as to unravel the underlying nuclear structure, is the broad aim of my work.
At very low temperatures there is a strong interplay between the shell (quantal fluctuations), statistical (thermal fluctuations), and residual pairing effects. At high-I, the pairing collapses but still the other two effects are strong and so is their interplay. In these cases, conclusive experimental results are scarce. We have constructed a theoretical framework to study the GDR with proper treatment of pairing and its fluctuations along with the thermal shape fluctuations. Our study reveals that the observed quenching of GDR width at low temperature in the nuclei 97Tc, 120Sn, and 179Au can be understood in terms of simple shape effects caused by the pairing correlations. For a precise match with the experimental data, the consideration of pairing fluctuations is crucial. I will demonstrate that more measurements with better precision could yield rich information about several phase transitions that can happen in warm nuclei.
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