Dynamics of Atomic and Molecular Metastable States Produced in Electron-Bombarded Superfluid Helium

We have studied the production, destruction, and lifetimes of the He₂(a³Σᵤ⁺) and He(2³S) metastable states of helium that are produced in electron-bombarded superfluid helium. The characteristic lifetime of a metastable molecule in the superfluid is shown to exceed 0.1 sec, while the lifetime of a metastable atom is only about 15 {μ}sec. The production rates for the He₂(a³Σᵤ⁺) and He(2³S) metastable states are about 500 and 450 per incident 160-keV electron, respectively.