CHEM_REACTION

PLASMAKIN Manual
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Syntax

&CHEM_REACTION [locus = 'Cvalue'] [,] {reaction = 'Cvalue'
| reactants = 'Cvalue' [[,]...] [,] products = 'Cvalue' [[,]...] [,] [opposing = Lvalue] [,] }
[comment = 'Cvalue'] [,] [efficiency = 'Cvalue',Rvalue [[,]...]] [,]
[ee_loss = Rvalue] [,] {value = Rvalue [[,]...] | data_file = 'Cvalue',Ivalue}
[,] [units = 'Cvalue'] /

Name	Description	Data type and attributes	Default value	Units or values supported
`locus`	Where the reaction takes place	CHARACTER(10)	`'gas'`	`'gas', 'user_string'`
`reaction`	Reaction equation	CHARACTER(80)	`''`
`reactants`	Reactant species	CHARACTER(20)	`NMaxReacSpc*''`
`products`	Product species	CHARACTER(20)	`NMaxReacSpc*''`
`opposing`	The NAMELIST describes both forward and reverse reactions	LOGICAL	`.FALSE.`	`.F`, `F`, `.f`, `f`, `.T`, `T`, `.t`, `t`
`comment`	Relation between vibrational quantum numbers	CHARACTER(20)	`''`
`efficiency`	List of species acting as 3rd body in 3-body collisions and relative efficiencies.	CHARACTER(20),REAL(8)	`NMax3bSpc*['',1.d0]`
`ee_loss`	Energy lost in the reaction by the electron	REAL(8)	`0`
`units`	Units used for reaction coefficient	CHARACTER(10)	`''`	`''`, `'s-1'`, `'m3s-1'`, `'cm3s-1''m6s-1'`, `'cm6s-1'`
`value`	Reaction rate equation coefficients	REAL(8)(12)	`(0, i=1,12)`
`data_file`	Index of function to compute the reaction rate in the user supplied `SetRate` routine.	DATA_COLUMN	`'',0`

Comments

The following rules must be followed:

If the locus of a reaction in the gas is indicated, this value must be 'gas'. For surface reactions any name can be used and reactions in different surfaces can be identified by different locus values.
The new reaction field to write the reaction equation replaces the use of the reactants, products and opposing fields. However the writing of the reaction equations must obey some rules:
1. The full equation must be enclosed in ' characters
2. Reactant or product species must be separated by + character with a space on both sides to differentiate from ionic species.
3. Direct reactions must be indicated by a single arrow, ->, while both direct and reverse reactions must be indicated by a double arrow, <->
If the reaction field is used, the other three fields are ignored.
All species indicated in the reaction or reactants and products lists must be described in a CHEM_SPECIES NAMELIST.
Reactions involving vibrational species can be collectively represented indicating the generic name representing the vibrational series. The vibrational species involved in the reaction can be selected through relational expressions involving the vibrational quantum numbers. These expressions can be included in the species name in the reaction field or, alternatively, in the reactants or products fields. If they involve two different vibrational quantum numbers they can also be indicated in the comment field. The vibrational quantum numbers in these expressions can only be represented by the letters v or w.
The following classes of relational expressions can be used:
1. If the reaction corresponds to a fixed variation of the vibrational quantum number, the relation between the initial and the final values can be translated into the names of the vibrational species in the reactants and products. In this case the arithmetic operators + and - can be used in the species names.
2. If the range of vibrational levels is defined by a relation involving only one vibrational number, this relation can be included in the vibrational series name.
3. If the expression used to select the vibrational levels involves two vibrational numbers, this relation must be written in the comment filed.
In case these two last cases the relations can be written using the logical operators <, ≤, =, ≥ and >. In the last case the modulo operator can also be used.
value is an array of 12 elements allowing representing the 6 pair of &agr;^j and &bgr;^j values needed to represent the rate coefficient using the equation indicated in chapter one.
If the vibrational rate coefficients must be computed from a table or analytically but the equation in chapter one is not adequate, the user can supply the external routine SetRate with user defined rate equations. The index value in the data_file field is used to selection of the appropriate rate equation. In this case the name value is not used.
The new field efficiency is used to indicate two lists used in 3-body reactions: a list of names of species taking part in the reaction as 3rd bodies and a list of the corresponding efficiencies.

Caution: Indistinguishable reactions

For a V-V reaction involving two vibrational levels of the same molecule the direct and reverse reactions are indistinguishable. In this case the opposing property should not be set to T. Otherwise the number of reactions is counted twice.

Examples

Example E-23. CHEM_REACTION: Example of CHEM_REACTION NAMELIST syntax.

  &CHEM_REACTION                                                          
    reaction = 'Ne[3P1] -> Ne + photon 1', value = 0.486e8 /

  &CHEM_REACTION
    reaction = 'Ne[3P2] + Ne[3P1] -> Ne + Ne+ + e',                       
    value = 3.2e-10, units = 'cm3s-1' /

  &CHEM_REACTION
    reactants = 'e','Ne', products = 'e','Ne[3P2]',                       
    units = 'cm3s-1', data_file = 'Ne_data.txt',3 /

  &CHEM_REACTION
    reaction = 'e + Ne[3P2] <-> e + Ne[3P1]',                             
    value = 1.603e-6, -0.3, -6.e2, 1, units = 'cm3s-1' /

  &CHEM_REACTION
    reaction = 'N2[X,v+1] + O2[X,w] -> N2[X,v] + O2[X,w+1]'
    data_file = "",1 /                                                    

  &CHEM_REACTION
    reactants = 'Ne','N2(X,v<=10)', products = 'Ne,2*'N'
    data_file = "",2 /                                                    

  &CHEM_REACTION
    reactants = 'N2[X,v]','M', products = 'N2[X,w]','M'
    comment = '|v-w|>=1', data_file = "",3 /

: Radiation emission; the value of value is the transition probability in s^-1.
: Penning ionisation with constant rate coefficient. Note the difference between the use of the plus sign to indicate the ion and the reaction members.
: Electron excitation. The values of the rate coefficient are read in the external file Ne_data.txt and identified by the index 3.
: Both the direct and reverse reactions are taken into account. The rate coefficient for the direct reaction has an Arrhenius temperature dependence with the above coefficients. The rate coefficient for the reverse reaction are automatically computed.
: Group of reactions on two vibrational series. The syntax for the relations between the vibrational quantum numbers corresponds to case a. above.
: Group of reactions involving a vibrational series. The syntax corresponds to case b. above.
: Group of reactions involving a vibrational series. the syntax corresponds to case c. above.

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CHEM_REACTION

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Syntax

Comments

Examples

`CHEM_REACTION`