SF6− photodetachment near the adiabatic limit

Abstract

High sensitivity photodetachment cross-section measurements of SF₆⁻ are performed near the adiabatic threshold limit. The extraction of adiabatic detachment energy (ADE) from the high sensitivity measurement of the cross-section change as a function of photon energy is discussed. Below the vertical detachment energy a steep 4 orders of magnitude cross-section drop is observed, with cross sections as low as 2 × 10⁻⁶ Ų measured for photon energies below 2 eV. The cross-section is fitted with both the expected spectral shape based on recently calculated Frank–Condon overlaps and a phenomenological threshold function. The resulting 1.7 ± 0.02 eV ADE values are significantly higher than previously recommended experimental ADE values obtained based on kinetics modeling, and possible differences between the experimental approaches are discussed.