Network used in Le Gal et al 2014

* Format
R1 + R2 = P1 + P2 + P3 + P4  alpha beta gamma Rtype Rid
format_network_write = '(2(a7,1x),"= ",4(a7,1x),3es12.3,i4,i6)'

* The last two integers are:
reaction type (i2)
reaction id   (i6)

* Reaction types:
 (1) : photo-reactions
 (2) : direct cosmic ray ionization or dissociation
 (3) : indirect cosmic ray ionization or dissociation
 (4) : cosmic ray induced desorption from grains
 (5) : H2, HD and D2 formation
 (6) : three body reactions on grain surfaces
 (7) : sputtering of grain mantles
 (8) : erosion of grain cores
 (9) : adsorption on grain surface
(10) : Collisional dissociation of H2
(11) : All other reactions
(12) : Grain neutralization
(13) : Grain charging

* Meaning of kinetic rates:

** For bimolecular reactions (11, 12, 13)
   k(T) = alpha*(T/300)**beta*exp(-gamma/T)

** Formation of H2 (or HD, D2) on grains is treated as a bimolecular
   reaction.

** Cosmic-ray ionization are splitted into direct and indirect
   (i.e. due to secondary photons). The value of gamma is irrelevant,
   and used only as a flag here.

* General References :
    [1] Flower et al., 1985, MNRAS 216, 775
    [2] Flower et al., 1986, MNRAS 218, 729
    [3] Pineau des Forêts et al., 1986, MNRAS 220, 801
    [4] Viala et al., 1988, A&A 190, 215