Challenges in Optical Cycling of Calcium Phenoxide

The laser cooling of large polyatomic molecules presents an exciting but formidable challenge due to their numerous vibrational and rotational degrees of freedom. Here, we build on previous high-resolution spectroscopy of the large polyatomic molecule calcium phenoxide (CaOPh) and report optical cycling of 2-5 photons on the molecule at a scattering rate of 13.7 kHz. This falls short of the estimated budget of 20 photons before decay to the first vibrational state, and at a scattering rate far below expectations. The cause of these observations has remained unexplained. We suggest several hypotheses which may explain the observed anomalies, and offer potential remedies for future studies.