Table A.1
Typical orders of magnitude for rates of PAH chemical processes in the diffuse ISM(a).
| Process | rate−1 | ref.(d) | Comments |
|---|---|---|---|
| yr | |||
| Photon absorption | 0.1 | 1 | 6–13.6 eV photons |
| Photoionization | 1 | 3 | |
| e− recombination | 1 | 4 | |
| 2nd photoionization | 3 | 5 | |
| H accretion(b) | 20 | 2 | |
| C+ accretion(b),(c) | 5 × 103 | 8 | |
| O accretion(b),(c) | 3 × 104 | 6 | |
| 2-photon absorption | 3 × 107 | ||
| CnHm accretion | >107 | 8 | Total accretion rate of |
| small C-rich molecules | |||
| He+ sputtering | ~108 | 7 | |
| PAH merging | ~108 |
Notes. (a) Reaction rates are estimated for a typical PAH/PAH+ of 50 C atoms in a diffuse interstellar cloud with nH = 50 cm−3, T = 50–100 K, UV intensity G0 = 3 Habing = 1.6 × 1014 erg cm−3. (b) Global PAH accretion rates have been divided by 2, assuming that neutral and cation PAH abundances are about half the total PAH abundance. (c) Assumed abundances:O 3.2 × 10−4; C+ 1.4 × 10−4.
References. (d) 1. Tielens (2013); 2. Andrews et al. (2016); 3. Leach (1996); 4. Montillaud et al. (2013); 5. Zhen (2016); 6. Snow & Bierbaum (2008); 7. Micelotta et al. (2010a); 8. this paper.
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