Radii and Collision Probabilities of Mestastable Neon and Mercury Atoms

Abstract

The problem of the life-time of metastable atoms was treated on the basis of the assumptions that (1) metastable atoms diffuse to the walls of the containing vessel and give up their energy there, and (2) metastable atoms perform impacts with other atoms and are either lowered to the normal state or raised to a higher state. The result was obtained that, for large values of the time elapsing after the cut-off of the excitation, the average number of metastable atoms per cc decays exponentially with the time, with an exponential constant equal to $\frac{A}{p}+Bp$ where $p$ is the pressure and $A$ and $B$ are constants containing the radius of the metastable atom and the probability of dissipative impact. The experimental results of Meissner and Graffunder, Eckstein, Zemansky and Pool are treated according to the theory, and values of the radius and probability are found. The radius in each case comes out smaller than the normal value, and the values of the probability are shown to substantiate the view that, in impacts between metastable atoms and either normal atoms of the same kind or foreign gas atoms whose first excitation potential is higher than the energy of the metastable atom, the metastable atom is raised to a state of higher energy.