Controlled Spinning of Molecules in Superfluid Helium using an Optical Centrifuge

An optical centrifuge is a shaped laser pulse that can be tuned to accelerate molecules to target rotational frequencies. We apply the centrifuge to molecules embedded in superfluid helium nanodroplets, enabling controlled rotational excitation of the defects inside a strongly interacting many-body environment. By measuring the alignment of the molecular distribution during the centrifuge, the accelerated rotation of molecules is directly observed over a continuous range of frequencies. With resonant excitation, measuring the decay rate of the centrifuge-induced alignment allows for time-domain measurements of rotational energy state lifetimes, even in the presence of rapid rotational decoherence. Current experiments using a new ultraslow optical centrifuge to map the molecule–helium interaction across the first few rotational states will be discussed.