New emission bands at high-density excitation of dense gas and liquid of helium irradiated by nitrogen ions

Abstract

Dense helium, whose atomic separation is several Å near 4 K, shows new emission bands following excitation by fast nitrogen ions. These new emissions can be classified into three groups, which grow and disappear stepwise with increasing pressure, accompanied with lifetime shortening except for a group at the highest density. They are explained as clusters of helium excimers.