Quantum-chemical insights into molecular few-body complexity

I will present examples of how molecular electronic structure and quantum scattering calculations can support and explain ultracold quantum physics experiments. Quantum-chemical calculations of potential energy curves, permanent and transition electric dipole moments, and fine and hyperfine coupling constants provide parameters for effective Hamiltonians describing nuclear dynamics. Multichannel quantum scattering calculations give scattering lengths and elastic, inelastic, and reactive rate constants. I will discuss the capabilities and limits of state-of-the-art methods applied to systems based on alkali-metal and alkaline-earth-metal atoms and present our recent results for ongoing experimental efforts, including chemical reactions between reactive alkaline-earth-metal dimers [1] and collisional losses of non-reactive molecules due to intermediate complex formation [2], as well as a detailed understanding of collision dynamics in atom-molecules systems [3].