Photoassociative spectroscopy of ultracold metastable argon

Abstract

We present results of photoassociative spectroscopy performed on ultracold metastable argon atoms in a magneto-optical trap. Ion spectra are obtained with laser detuning up to a few gigahertz below the $4s[3/2]{}_{2}\ensuremath{\rightarrow}4p[5/2]{}_{3}$ trapping transition at 811 nm and with intensities in a range of $~({10}^{2}\ensuremath{-}{10}^{5}){I}_{\mathrm{Sat}}$. We also compute dipole-dipole potentials for both singly and doubly excited diatomic molecules and use a Leroy-Bernstein analysis to determine the approximate vibrational spacings in the ($s+p$) and ($p+p$) manifolds. Based on this theoretical framework, we explain a broad background feature in our data and suggest that double-excitation mechanisms are likely responsible for sharp dips in the ion signal.