31 Oct. 2002
Added description and comments. Tatiana

## Numbering Rules ( ITYPE ) for reaction types in 
   CDDATA,   JCDDATA,  qdata  etc.
The original version (1990 - 1991 Aug) is in directory z/zjmemo.txt.
This file has been updated and modified at OSU since 1991 Sept.
Notes for changing eqwrt.f  are  found in eqwrt.memo .


		Numbering rules for reactions.
==========================================================================
ITYPE		Reaction Type
-------------------------------------------------------------------------
 0	Gas-grain interaction, electron-grain recombination (old version)
 1	Cosmic Ray ionization. A(J)=scaling factor
 2	Ion-melecule reactions and charge exchange reactions.
 3	Negative ion - neutral species  reactions
 4	Radiative association:  ion-neutral
 5	Electron ejection:	negative ion - neutral
 6	neutral + neutral -->	ion + electron	  (only one reaction)
 7	Neutral + Neutral chemical reaction.
 8	Neutral + Neutral radiative association.
 9	Dissociative recombination.
10	Radiative recombination (No dissociation) atomic,molecular ion + e.
11	Positive-ion  .vs. Negative-ion Recombination.
12	Electron attachment (neutral + e --> negative ion)
13	Photo-ionization   and   photo-dissociation.
14	Grain-surface chemical reactions
	  Activation energy is given as C(J) for ITYPE=14, 
	  if it may not be used in the program.
15	Thermal evaporation. JX-->X. All finite values were used in jcddata3.1
          Adsorption energy is to be given here as C(J) and is used for 
	  various purposes.
16	Cosmic Ray induced general desorption         JX -> X
	  ==> Plan changed. ED dependent CR induced classical desorption.

17 	Photodissociation by cosmic rays	
	JNO -> JN + JO 	corresponds to 	NO -> N + O
18 	Photodissociation by cosmic rays
	JNO -> JN + JO	corresponds to	NO -> NO+ + E
19	Photodissociation by background photons
	JC2 -> JC + JC	corresponds to 	C2 -> C + C
20	Photodissociation by background photons
	JC2 -> JC + JC	corresponds to C2 -> C2+ + E

##	Chemi-desorption (Reaction products only, or selective desorption)
##	General (indiscriminate) desorption due to formation energy. 
##	Photo-desorption (discriminate or indiscriminate)

97	Dummy: surface -> mantle  transition. JX -> QX
98      Dummy: mantle  -> surface transition. QX -> JX
99      Dummy: gas     -> surface accretion.   X -> JX
	May be made meaningful if appropriate.
          ---> Currently,  X--->JX are treated as 99. 
	Actural Accretion Term in program = Q(I). [schem.f, jchem.f, qchem.f]
Q(I)	Gas accretion onto grains (sticking)
------------------------------------------------------------------------------

Naming rules.
All file names related to surface chemistry begin with   j,    viz.
JCO = surface CO,    QCO = manltle CO.

jchem2.f	= main routine version 2 etc. jchem1.f was developed from 
		    schemv4.f 
jcdfr3.f	= sub FCHM10 ,,, sub RATES,,,,,  etc. corresponds to scdfr.f
jcddata		= input deck, similar to cddata
jcdout or jout	= output file, similar to cdoutput

Mantle/surface species are separated in files whose name begin with q.

qchem1.f	=main routine, developed from jchem9.f
qcdfr1.f
qdata1.1
qout
----------------------------------------------------