Fig. 2: Dependence of reaction rate on rotational state.

a Scatter plot showing reaction rate outcomes from repeated measurements for uncontrolled and super-rotor SiO⁺. Dotted lines indicate the average of each set. All measurements were taken at the same pressure and corresponding to an estimated H₂ number density of 7 (1) × 10⁶ cm⁻³. b Theoretical and experimental relative rate enhancement as a function of the SiO⁺ rotational quantum number. Relative experimental rates are calculated with respect to the case of no optical pumping (purple data point). Vertical error bars represent the 1σ statistical uncertainty. Horizontal error bars are the spread in prepared rotational distribution (with the spread encompassing more than 90% of the SiO⁺ population). Explanations for theory calculations stopping at j=140 are discussed in the text (see section “Reaction rates”).