Second excited state of ${}^4\mathrm{He}$ tetramer

TL;DR

This paper predicts and characterizes a second excited state of the helium-4 tetramer, a resonance observable in atom-trimer scattering, using rigorous momentum-space calculations with realistic potentials.

Contribution

It provides the first detailed calculation of the second excited tetramer's resonance properties in helium-4, including finite-range effects and contributions from multiple partial waves.

Findings

Resonant behavior observed below the trimer threshold

Position and width of the resonance determined

Finite-range effects significantly influence the width

Abstract

The four-boson universality suggests the existence of the second excited tetramer state in a system of cold ${}^4\mathrm{He}$ atoms. It is not bound but could be seen as a resonance in the atom-trimer scattering. This process is rigorously calculated using the momentum-space transition operator framework with two realistic interatomic potentials. The $S$-wave phase shift and cross section show a resonant behavior below the excited trimer threshold, but there are sizable nonresonant contributions from $P$ and $D$ waves as well. The position and width of the resonant state is determined, and for the latter significant finite-range effects are found.