Lifetimes of Metastable States of Noble Gases

The lifetimes of the lower metastable states of helium, neon, and argon have been studied as a function of the pressure and temperature of the parent gas and the size of the container. The lifetimes were determined from measurements of the decay constant of the radiation absorbed by the metastable atoms. At low metastable concentrations the loss is by diffusion to the walls of the absorption cell and by collisions with neutral atoms within the volume of the cell. The data indicate that at 300^ and sufficiently high pressures, the volume destruction of the lower neon metastable is directly proportional to the pressure as expected for two-body collisions. The volume destruction of the lower neon metastables at 77^ and the helium triplet metastables at 300^ and 77^ is proportional to the square of the pressure as for three-body collisions. The volume loss of the lower argon metastables at 300^ contains both linear and quadratic pressure dependent terms.