Determination of H⁺+Cs(6s) potential from differential cross section measurements at energies 13.4-24.2 eV

The relative differential cross sections for elastic scattering of H + by a caesium vapour has been measured. The reduced cross sections exhibit a characteristic rainbow oscillatory structure. The rainbow reduced-scattering angle is 63.5+or-1.4 eV deg. A best Morse potential has been determined by fitting the experimental data with semiclassical differential cross sections. The well depth of the Cs(6s)H + Morse potential is 0.77+or-0.05 eV at 10+or-1 a 0 , the exponential parameter being 2.5+or-0.1. For comparison the Cs(6s)H + molecular potential has been calculated using a pseudopotential approach with a large LCAO-MO basis. The interaction of the valence electron with the Cs + ion is represented by a Hellmann pseudopotential. When the non-linear coefficients of the trial wavefunction are optimised, satisfactory agreement is obtained with the experimentally determined potential.