Calculated Spectrum of Quasibound States for H2(1Σg+) and Resonances in H + H Scattering

Abstract

The Born—Oppenheimer potential of Koℏos and Wolniewicz for H₂(¹Σ_g⁺) was fitted (±0.7 cm⁻¹) by a polynomial, and the complete spectrum of bound and quasibound states was computed by direct numerical integration of the radial Schrödinger equation. The short‐lived virtual states were studied via the energy dependence of the resonant phase shifts, following Buckingham, Fox, and Gal. Of the total of 301 bound states, the 108 levels observed by Herzberg and Howe were reproduced by the computations with an average deviation of ∼3.6 cm⁻¹ (maximum deviation of 5.3 cm⁻¹). Of the two observed quasibound states, the lower was satisfactorily reproduced, but for the upper one, the computed value deviated by 5.3 cm⁻¹; in addition the calculated width was inconsistent with the sharpness of the observed level. Thus it is inferred that a small change in the potential (e.g., a drop of ∼5 cm⁻¹ near R=3 a.u.) is required. Of the shortest‐lived quasibound states, 10 have fractional widths Γ/E in the range 0.01–0.1, and are thus possibly suitable for observation as resonances in singlet atom—atom scattering. Collision energies for these range from 0.011 to 0.93 eV.