Statistical quantum mechanical approach to diatom–diatom capture dynamics and application to ultracold KRb + KRb reaction

A general and rigorous quantum method is proposed for studying capture dynamics between two diatomic molecules in full dimensionality. By solving the time-independent Schrödinger equation with proper boundary conditions, this method is ideally suited for studying quantum dynamics of cold and ultracold reactions. To illustrate its applicability, the capture dynamics between ultracold KRb molecules is characterized in full six dimensions for the first time using a first-principles based long-range interaction potential. The calculated capture rates for collisions involving distinguishable and indistinguishable ⁴⁰K⁸⁷Rb molecules are in good agreement with the experiment and exhibit clear Wigner threshold behaviors. Predictions for ultracold collisions between internally excited ⁴⁰K⁸⁷Rb suggest minor changes in the loss rate, consistent with experimental observations in similar systems.