Small helium clusters formation

We investigated small helium clusters formation in nonequilibrium conditions using the non-Hermitian formalism. Helium is a simple enough system for analytical study while complicated enough to have a rich variety of quantum properties. In this article, we used a new formalism based on non-Hermitian quantum mechanics for describing the electronic excited states in clusters. This formalism enabled to estimate the decay time of excited states within a single scheme. Its implementation to helium shows the existence of new long-lived excited states in small helium clusters at the distance of 5.6 Bohr radii between atoms. Moreover, several helium excimers and exciplexes at the distances between helium atoms of 35.5, 22.8, 14.0, and 8.5 Bohr radii with the scaling factor of about 1.6 were found. It is related to the restructuring of the electronic structure caused by powerful external excitations. These results give a new insight on clustering processes providing more profound and complete understanding.