Extended Data Fig. 1: First order reaction rate constants obtained from the kinetic profiles of (a) m/z 104, (b) m/z 105, (c) m/z 106 and (d) m/z 130 plotted against the acetylene number density.

Second order reaction rate coefficients are obtained using a linear fit to obtain (a) k₂, (b) k_RA, (c) k_proto and (d) k_2,C7. When using large acetylene number densities, required for the measurements on m/z 106 and 130, the reaction towards m/z 104 and 105 has almost proceeded completely during the helium pulse phase (which is not included in the fit) and yields a larger fit error for the latter. The error bars indicate the 1σ errors and the grey shaded bands define the 2σ uncertainty regions of the fits.