Fig. 3.

TD-ID-CIMS composition analysis of nano-sized particles formed from the ternary nucleation of the H₂SO₄-CPA-H₂O system. Ion signals for HSO₄⁻, HSO₄⁻·H₂SO₄, CPA·O₂⁻, and HSO₄⁻·CPA, representing H₂SO₄, H₂SO₄-H₂SO₄ dimer, CPA, and CPA-H₂SO₄ dimer, respectively. The reagent ions were CO₃⁻ (60 amu) and CO₄⁻ (76 amu). The collected particle mass was heated at ≈2 min. To ensure a sufficient mass was collected, the particle size ranged from 3 to 13 nm, with a peak diameter of ≈7 nm and a peak concentration (dN/dDp) of 10⁷. The ratio between CPA and H₂SO₄ was estimated to be ≈1 to1,000 in the collected particle mass. In our experiments, it took ≈4 h to collect a ≈150 ng particle mass, assuming a 10% overall charging efficiency and a particle density of 1.5 g cm⁻³.