Table 3 Calculated rate constants of possible oxyacid sources (T = 295 K).

From: A gas-to-particle conversion mechanism helps to explain atmospheric particle formation through clustering of iodine oxides

Reaction

k MESMER

k upper-limit experimentale

30 Torr

760 Torr

I + H2O → H2O…I

2.4 × 10−13 cm3 s−1

4.7 × 10−12 cm3 s−1

 

H2O…I → I + H2O

1.7 × 106 s−1

3.4 × 107 s−1

 

H2O…I + O3 → HOIO/HOIO2 + HO2/OH

100 s−1

100 s−1a

 

I + H2O ( + O3)→ HOIO/HOIO2 + HO2/OH

2.8 × 10−19 cm3 s−1

2.1 × 10−19 cm3 s−1

2.8 × 10−19 cm3 s−1 (a, e)

IO + H2O → H2O…IO

1.9 × 10−15 cm3 s−1

4.6 × 10−14 cm3 s−1

 

H2O…IO → IO + H2O

1.6 × 107 s−1

4.0 × 108 s−1

 

H2O…IO + O3 → HOIO2 + HO2

100 s−1

100 s−1b

 

IO + H2O ( + O3) → HOIO2 + HO2

2.0 × 10−21 cm3 s−1

2.0 × 10−21 cm3 s−1

2.0 × 10−20 cm3 s−1

I2O2 + H2O → HOI + HOIO

  

1 × 10−19 cm3 s−1 (b)

I2O3 + H2O → HOI + HOIO2

2.3 × 10−20 cm3 s−1

 

2 ×  10−18  cm3 s−1 (c)

 

Eckart tunnelingc: 3.8 × 10−19 cm3 s−1

  

I2O4 + H2O → HOIO + HOIO2

9.3 × 10−16 cm3 s−1

8.0 × 10−16 cm3 s−1

5 × 10−19 cm3 s−1 (d)

→ HOIO…HOIO2d

0.2 × 10−16 cm3 s−1

1.4 × 10−16 cm3 s−1

 
  1. aAdjusted to obtain a net rate constant equal to the effective rate constant determined by resonance fluorescence with the ROFLEX machine. For [O3] = 2.5 × 1012 molecule cm−3 (100 ppbv at 760 Torr), the corresponding rate constant would need to be: k = 4 × 10−11 cm3 s−1 molecule−1.
  2. bThe same loss rate of the I-water adduct is assumed for the IO-water adduct.
  3. cQuantum-mechanical tunneling is incorporated in the master equation using a parabolic Eckart-type barrier39,61.
  4. dThe HOIO…HOIO2 potential well is deep enough to enable collisional stabilization of the adduct at high pressure. We have no evidence of a peak at m/z = 336 in our high-pressure mass spectra.
  5. eBold letters in brackets refer to the panel of Fig. 6 in the main text showing the simulation from which the upper limit is obtained. For I2Oy + H2O, the upper limit is better constrained by the experiment at 450 Torr with 10.5 eV PI photon energy (thee co-products HOI and HOIO have ionization energies below 10.5 eV).
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