Automated detection of laser cooling schemes for ultracold molecules

Ultracold molecules offer exciting prospects for quantum sciences, including quantum chemistry, sensing, and simulations. Their applications are, however, limited by the challenges in their cooling. So far, there were two main approaches to producing ultracold molecules: either by combining already ultracold atoms (resulting in, e.g., KRb and NaCs) or by laser cooling species with quasidiagonal Franck-Condon factors (like SrF, CaF, and YO). Those ultracold species are far from being chemically typical, and thus their applications are limited outside fundamental physics.

Recently, a laser cooling scheme was found for the carbon dimer [1], proving that laser cooling is possible for species with strongly off-diagonal Franck-Condon factors. A manual search for such schemes across complex molecular energy levels is challenging. Here, we report the development of a graph-based algorithm allowing for the automated detection of laser cooling schemes out of energy levels and allowed transition data accessible for a range of molecular species in the Exomol database. We rediscovered a found laser cooling scheme for the carbon dimer and proposed more. Analysis of other molecular species is on the way. This work paves the way for ultracold molecules with new applications, in particular in astrochemistry.

[1] N. Bigagli, D. W. Savin, & S. Will. Laser cooling scheme for the carbon dimer (¹²C₂). Phys. Rev. A 105, L051301 (2022)