CH + H2 (+M) -> CH3 (+M)

k_inf = 1.98E+12 T^(.43) exp(370 cal/mol /RT)cm3/mol s

F_cent = (1-0.578) exp(-T/122) + 0.578 exp(-T/2535) + exp(-9365/T)

Third-body efficiencies:

SOURCE:

Two channel RRKM calculations for CH3 decomposition, following the work of Wagner and Harding (1992). (A. F. Wagner, private communication, 1996) The related reactions of this system are 50 H + CH2 (+M) = CH3 (+M), and the chemical activation 126 CH + H2 = H + CH2.

< delta-E> (average energy transferred per collision) = 0.30 kcal/mol
The Lennard-Jones parameters: sigma (CH3-N2) = 3.78 A, epsilon = 103 K
I+/I (used to compute the Waage-Rabinovitch correction for rotational energy) = 6.8
v = 3184, 3184, 3000, 1383, 1383, 580 cm^(-1)

COMMENTS:

The recent k_inf measurements of Brownsword et al (1997) up to 744K are just 10% greater than this expression. Values for k_o(Ar) agree within 20%.

A comparison with high temperature data for the reverse decomposition reaction, k_o in Ar, is shown in the figure.

The pressure broadening is expressed in the Troe form.in

Included in the mechanism for version 3.0, where it served as an optimization variable. The final rate expressions are 0.50 times the original base values.

REFERENCES:

Rohrig et al (1997)

Rohrig, M., Petersen, E.L., Davidson, D.F., Hanson, R.K., and Bowman, C.T. (1997) Int. J. Chem. Kinet. 29 , 781.

Brownsword et al (1997)

Brownsword, R.A., Canosa, A., Rowe, B.R., Sims, I.R., Smith, I.W.M., Stewart, D.W.A., Symonds, A.C., and Travers, D. (1997) J. Chem. Phys. 106, 7662.

Markus et al. (1996)

Markus, M.W., Roth, P., and Just, Th. (1996) Int. J. Chem. Kinet. 28 , 171.

Lim and Michael (1994)

Lim, K.P., and Michael, J.V. (1994) 25th Symposium (International) on Combustion, p. 713.

Kiefer and Kumaran (1993)

Kiefer, J.H. and Kumaran S.S. (1993) J. Phys. Chem. 97, 414.

Dean and Hanson (1992)

Dean, A.J., and Hanson, R.K. (1992) Int. J. Chem. Kinet. 24 , 517.

Markus et al. (1992)

Markus, M.W., Woiki, D., and Roth P. (1992) 24th Symposium (International) on Combustion, p. 581.

Troe (1977)

Troe, J. (1977) J.Chem.Phys. 66, 4745.

Wagner and Harding (1992)

Wagner, A.F., and Harding, L.B. (1992) ACS Symp. Ser. 502, 48.

                        PRESSURE = 0.1 atm N2  
______________________________________________________________________
    Temp      delta-S     delta-H      kf          kr         Keq     
     (K)    (cal/mol K)  (kcal/mol) ----(mol,cm3,s)-----   (cm3/mol)  
______________________________________________________________________
                                                                      
     300       -27.5      -110.8    4.87E+12    1.32E-64    3.69E+76
     500       -29.5      -111.5    1.26E+12    6.20E-34    2.04E+45
    1000       -31.2      -112.7    1.33E+11    2.07E-11    6.41E+21
    1500       -31.6      -113.2    3.13E+10    1.20E-04    1.01E+14
    2000       -31.6      -113.3    1.08E+10    7.85E-01    1.37E+10
    2500       -31.6      -113.2    4.71E+09    6.75E+01    6.96E+07
    3000       -31.5      -113.0    2.40E+09    1.13E+04    2.13E+06
______________________________________________________________________


                        PRESSURE = 1 atm N2    
______________________________________________________________________
    Temp      delta-S     delta-H      kf          kr         Keq     
     (K)    (cal/mol K)  (kcal/mol) ----(mol,cm3,s)-----   (cm3/mol)  
______________________________________________________________________
                                                                      
     300       -27.5      -110.8    1.57E+13    4.24E-64    1.85E+76
     500       -29.5      -111.5    6.85E+12    3.36E-33    1.02E+45
    1000       -31.2      -112.7    1.08E+12    1.68E-10    3.21E+21
    1500       -31.6      -113.2    2.69E+11    2.66E-03    5.05E+13
    2000       -31.6      -113.3    9.45E+10    6.90E+00    6.85E+09
    2500       -31.6      -113.2    4.17E+10    6.00E+02    3.48E+07
    3000       -31.5      -113.0    2.15E+10    1.01E+04    1.07E+06
______________________________________________________________________


                        PRESSURE = 10 atm N2   
______________________________________________________________________
    Temp      delta-S     delta-H      kf          kr         Keq     
     (K)    (cal/mol K)  (kcal/mol) ----(mol,cm3,s)-----   (cm3/mol)  
______________________________________________________________________
                                                                      
     300       -27.5      -110.8    3.15E+13    8.50E-64    3.69E+76
     500       -29.5      -111.5    1.81E+13    8.85E-33    2.04E+45
    1000       -31.2      -112.7    5.65E+12    8.80E-10    6.41E+21
    1500       -31.6      -113.2    1.87E+12    1.85E-02    1.01E+14
    2000       -31.6      -113.3    7.20E+11    5.25E+01    1.37E+10
    2500       -31.6      -113.2    3.30E+11    4.74E+03    6.96E+07
    3000       -31.5      -113.0    1.75E+11    8.25E+04    2.13E+06
______________________________________________________________________

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