Trapping molecular ions formed via photo-associative ionization of ultracold atoms

Abstract

The formation of ⁴⁰Ca₂⁺ molecular ions is observed in a hybrid ⁴⁰Ca magneto-optical and ion trap system. The molecular ion formation process is determined to be photo-associative ionization of ultracold ⁴⁰Ca atoms. A lower bound for the two-body rate constant is found to be ≥ 2 ± 1 × 10⁻¹⁵ cm³ Hz. Ab initio molecular potential curves are calculated for the neutral Ca₂ and ionic Ca₂⁺ molecules and used in a model that identifies the photo-associative ionization pathway. As this technique does not require a separate photo-association laser, it could find use as a simple, robust method for producing ultracold molecular ions.