Table 1
Reactions, rate data and related parameters for the N2H+ chemical network.
| Reaction | ζ a | α b | β b | γ b | S c | Eb d | Y e | k0(r,z) f |
| (s-1) | (cm3 s-1) | (K) | (K) | (photon-1) | (s-1) | |||
|
|
||||||||
H2 + cosmic ray → H + e− |
1.20 × 10-17 | ... | ... | ... | ... | ... | ... | ... |
H + H2 → H + H |
... | 2.08 × 10-9 | 0 | 0 | ... | ... | ... | ... |
| H + e− → H2 + H |
... | 2.34 × 10-8 | –0.52 | 0 | ... | ... | ... | ... |
N2 + H N2H+ + H2 |
... | 1.80 × 10-9 | 0 | 0 | ... | ... | ... | ... |
| CO + H HCO+ + H2 |
... | 1.36 × 10-9 | –0.14 | –3.4 | ... | ... | ... | ... |
| N2H+ + CO → HCO+ + N2 | ... | 8.80 × 10-10 | 0 | 0 | ... | ... | ... | ... |
| HCO+ + e− → CO + H | ... | 2.40 × 10-7 | –0.69 | 0 | ... | ... | ... | ... |
| N2H+ + e− → N2 + H | ... | 2.77 × 10-7 | –0.74 | 0 | ... | ... | ... | ... |
| CO → CO (ice) | ... | ... | ... | ... | 0.90 | ... | ... | ... |
| N2→ N2 (ice) | ... | ... | ... | ... | 0.85 | ... | ... | ... |
| CO (ice) → CO | ... | ... | ... | ... | ... | 855 | ... | ... |
| N2 (ice) → N2 | ... | ... | ... | ... | ... | 800 | ... | ... |
| CO (ice) + hν → CO | ... | ... | ... | ... | ... | ... | 1.4 × 10-3 | ... |
| N2 (ice) + hν → N2 | ... | ... | ... | ... | ... | ... | 2.1 × 10-3 | ... |
| CO + hν→ C + O | ... | ... | ... | ... | ... | ... | ... | 4.4 × 10-7 |
| N2 + hν→ 2 N | ... | ... | ... | ... | ... | ... | ... | 3.9 × 10-7 |
Notes. Equations for the reaction rate coefficients or reaction rates can be found in Appendix A. Photodesorption processes are shown in gray and are only considered in model CH-PD. For photodissociation the unshielded rates are listed.
Cosmic ray ionization rate taken from Cravens & Dalgarno (1978).
Values taken from the rate12 release of the UMIST database for Astrochemistry (McElroy et al. 2013).
Lower limits for the sticking coefficients taken from Bisschop et al. (2006).
Binding energies for pure ices taken from Bisschop et al. (2006).
Photodesorption yields. For CO, the yield is taken from Paardekooper et al. (2016) for CO ice at 20 K. For N2, the result from Bertin et al. (2013) for mixed ices with CO:N2 = 1:1 in protoplanetary disks is used. The yield for CO under these conditions is similar to the one reported by Paardekooper et al. (2016).
Unattenuated photodissociation rates for the adopted radiation field at a disk radius of 25 AU. Unshielded photodissociation rates for CO are taken from Visser et al. (2009) and for N2 from Li et al. (2013) and Heays et al. (2014).
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