Knowledge Bank

Differential cross sections for elastic scattering of electronically excited metastable Ne and Ar atoms by ground state it have been measured at two collision energies, $E=1.4$ and 2.7 kcal/mole, using crossed supersonic atomic beams. Observed peaks in the cross sections correspond to a well known but hitherto unobserved singularity in the Jacobian factor for the center-of-mass $\to$ laboratory intensity transformation. The measurements have been fitted to a modification of the exp-6 potential, and portions of the repulsive interactions have been determined. The derived potentials are similar to one previously found for Li-He, but display a definite deviation from exponential behavior inside $r\sim 3$ {\AA}. It is speculated that the may be due to an attractive interaction between He and the ionic core of the metastable atom.