Extended Data Fig. 8. Four experiments that demonstrate the influence of acids and NO_x on IP-OOM nucleation at −50 °C.

Four experiments showing nucleation rates at 1.7 nm, J_1.7, measured at similar IP_0N concentrations, 1.2–3.3 × 10⁷ cm⁻³, but with added acids, NO_x and acids + NO_x, respectively. The marker area is proportional to the IP_0N concentration. The experimental conditions are shown next to the data points. Circles correspond to absence of acids and squares include acids. The data show that extremely low H₂SO₄ concentrations, 1.3–2.8 × 10⁶ cm⁻³, strongly enhance the nucleation rates regardless of the absence or presence of NO_x. On the other hand, additions of high nitrate IP-OOM concentrations around 10⁸ cm⁻³ only produce relatively small increases in nucleation rates.