Potential energy surface and bound states of the (X4Σ)KRb-K complex

Abstract

We present in this work a potential energy surface of the (X4R)KRb-K complex for which high level ab initio calculations have been carried out at the RCCSD(T) level of theory, using ECP10MDF/ECP28MDF effective core potentials and basis sets for K/Rb, respectively, with the dimer at its lowest triplet 3Sigma state and fixed to the equilibrium distance. The interaction is shown to be very anisotropic, with one clear minimum at a T-type geometry of the complex. The depth of the well is found to be 767.7 cm-1 located at R=4,60 angstroms and theta=105 degrees in Jacobi coordinates from the center of mass of the diatomic partner. A variational (VAR) procedure and the Diffusion Monte Carlo technique have been applied to explore the bound states of the aggregate. Both descriptions provide similar features for the vibrational, nonrotating, ground-state, with an energy of -737,8 cm-1 and the maximum of the wavefunction peaked above the well of the surface. Excited states are also reported using the VAR treatment and angular and/or radial excitations are identified among the lower-lying vibrational states. These results should already provide an initial step toward a more comprehensive study of the collisions at ultralow temperatures of K+KRb, important process in the field of ultracold molecular chemistry.