Progress toward ultracold chemistry: Ultracold atomic and photonic collisions

The dynamics of ultracold quantum gases composed of atoms or molecules with extremely low translational energy E_t/k_B ≪ 1 millikelvin is dominated by the long-range mutual interactions between particles. Such studies require a detailed modelling of the atom-molecule or molecule-molecule long-range interactions inside the quantum gas with or without the presence of external fields. This paper focuses on two particular aspects relevant to ultracold chemistry: (i) The calculation of rates for photoassociation of a cold atom and a cold molecule to create ultracold excited trimers, based on the knowledge of the long-range interaction between the two species, showing that such rates are encouraging under the density and temperature conditions of a nearly degenerate quantum gas; (ii) The determination of the long-range interactions between two identical polar bialkali molecules in their rovibronic ground level in the presence of an electric field, showing the possibility for the formation of ultracold polar tetramers by stimulated emission.