2026 Theses Doctoral

Laser Cooling and Magneto-Optical Trapping of Diatomic Metal Hydrides and Deuterides

Dai, Jinyu

Laser cooling plays an important role in modern atomic, molecular, and optical physics. Since its first demonstration, it has initiated a variety of research directions in quantum science and technology. The first Bose-Einstein condensate, multiple platforms for quantum simulation and computation, ultracold quantum chemistry, and high-precision measurements of fundamental constants, all rely on the ability to cool atoms to temperatures near absolute zero. However, laser cooling has long been limited to atoms, and molecular laser cooling techniques have only been developed in the past decade.

In this thesis, I describe the extension of these techniques to a new class of molecules: diatomic metal hydrides. We demonstrate one-dimensional laser cooling of calcium monohydride (CaH) molecules and characterize their unique predissociative loss channels. With an optimal laser cooling scheme, efficient laser slowing is realized and a three-dimensional magneto-optical trap (MOT) of CaH is created. Future improvements of the MOT and prospects for cooling to ultracold temperatures are discussed. With a proposed coherent dissociation pathway, ultracold atomic hydrogen could be produced with even colder temperatures than the parent CaH molecules, potentially enabling optical trapping of hydrogen for precision spectroscopy.

Additionally, given its relatively low number of electrons, CaH is one of the first molecules that could be treated fully quantum mechanically in computational quantum chemistry. Ultracold CaH is a powerful platform to benchmark such theoretical frameworks. Finally, I describe how a similar approach can be implemented for its fermionic isotopologue, calcium monodeuteride (CaD). One-dimensional laser cooling of the fermionic CaD is demonstrated for the first time.