# Decoherence of collective motion in warm nuclei

## TL;DR

This paper investigates how collective nuclear states lose coherence with increasing excitation energy, affecting phenomena like rotational damping and magnetic radiation, and introduces new examples and interpretations of these effects.

## Contribution

It presents new insights into decoherence mechanisms in warm nuclei, including a novel oblate band example and the transition from coherent to damped magnetic rotation.

## Key findings

- Decoherence reduces collective coherence with excitation energy.
- A new oblate band exemplifies screening from rotational damping.
- Incoherent thermal M1 radiation (LEMAR) appears at zero energy in spherical nuclei.

## Abstract

Collective states in cold nuclei are represented by a wave function that assigns coherent phases to the participating nucleons. The degree of coherence decreases with excitation energy above the yrast line because of coupling to the increasingly dense background of quasiparticle excitations. The consequences of decoherence are discussed, starting with the well studied case of rotational damping. In addition to superdeformed bands, a highly excited oblate band is presented as a new example of screening from rotational damping. Suppression of pair correlation leads to incoherent thermal M1 radiation, which appears as an exponential spike (LEMAR) at zero energy in the $\gamma$ strength function of spherical nuclei. In deformed nuclei a Scissors Resonance appears and LEMAR changes to damped magnetic rotation, which is interpreted as partial restoration of coherence.