Precisely spun super rotors

Improved optical control of molecular quantum states promises new applications including chemistry in the quantum regime, precision tests of fundamental physics, and quantum information processing. While much work has sought to prepare ground state molecules, excited states are also of interest. Here, we demonstrate a broadband optical approach to pump trapped SiO + molecules into pure super rotor ensembles maintained for many minutes. Super rotor ensembles pumped up to rotational state N = 67, corresponding to the peak of a 9400 K distribution, had a narrow N spread comparable to that of a few-kelvin sample, and were used for spectroscopy of the previously unobserved C 2 Π state. Significant centrifugal distortion of super rotors pumped up to N = 230 allowed probing electronic structure of SiO + stretched far from its equilibrium bond length. Optical pulses can be useful to create and control molecules in higher quantum states. Here the authors use optical pumping to create rotationally excited states of SiO + molecular ion into super rotor ensemble.