Table 4: The main reactions and their reaction rates. The $\dagger $ marks reactions for which rate coefficients have been derived in this work. Coefficients which have been derived during this work are printed in bold, while previous estimates for these coefficients are printed in italics.
Reactants $\longrightarrow$ Products Rate coefficent [s-1] Reference
C2H6 + $h\nu$ $\longrightarrow$  C2H5 + H     3.28 $\times$ 10-6 (Huebner et al. 1992)
C2H6 + $h\nu$ $\longrightarrow$  C2H4 + H2     3.67 $\times$ 10-6 (Huebner et al. 1992)
C2H6 + $h\nu$ $\longrightarrow$ CH3 + CH3     8.80 $\times$ 10-7 (Huebner et al. 1992)
C2H6 + $h\nu$ $\longrightarrow$ CH2 + CH4     2.22 $\times$ 10-6 (Huebner et al. 1992)
C2H5 + $h\nu$ $\longrightarrow$  C2H2 + H2 + H 1.00 $\times$ 10-6 (Boice 2000, pers. comm.)
C2H4 + $h\nu$ $\longrightarrow$  C2H2 + H2     2.40 $\times$ 10-5 (Huebner et al. 1992)
C2H4 + $h\nu$ $\longrightarrow$  C2H2 + H + H 2.30 $\times$ 10-5 (Huebner et al. 1992)
C2H4 + $h\nu$ $\longrightarrow$ CH2 + CH2     6.00 $\times$ 10-5 (Huebner et al. 1992)
C2H2 + $h\nu$ $\longrightarrow$ $\rm C_2$ + H2     2.74 $\times$ 10-6 (Huebner et al. 1992)
C2H2 + e $\longrightarrow$ $\rm C_2$ + H2 + e 1.90 $\times$ 10-8 (Schmidt et al. 1988)
C2H2 + $h\nu$ $\longrightarrow$ $\rm C_2H$ + H     1.02 $\times$ 10-5 (Huebner et al. 1992)
C2H2 + e $\longrightarrow$  C2H + H + e 1.90 $\times$ 10-8 (Schmidt et al. 1988)
C2H + $h\nu$ $\longrightarrow$ $\rm C_2$ + H     3.00 $\times$ 10-5 (Huebner et al. 1992)
$\rm C_2$ + $h\nu$ $\longrightarrow$ C + C     1.40 $\times$ 10-7 (Huebner et al. 1992)
$\rm C_2$ + $h\nu$ $\longrightarrow$ C2+ + e     9.10 $\times$ 10-7 (Huebner et al. 1992)
$\rm C_2$ + e $\longrightarrow$ C + C + e 9.43 $\times$ 10-10 (Schmidt et al. 1988)
C3H4 + $h\nu$ $\longrightarrow$  C3H3 + H     1.33 $\times$ 10-4 Moses (2000, pers. comm.)
C3H4 + $h\nu$ $\longrightarrow$  C3H2 + H2     2.96 $\times$ 10-5 Moses (2000, pers. comm.)
C3H4 + e $\longrightarrow$ C3 + H2 + H2 + e 3.80 $\times$ 10-8 (Schmidt et al. 1988)
C3H3 + $h\nu$ $\longrightarrow$  C3H2 + H     1.82 $\times$ 10-3 Moses (2000, pers. comm.)
$\dagger $ C3H2 + $h\nu$ $\longrightarrow$ C3 + H2     9.50 $\times$ 10-7 Helbert [this work]
C3H2 + $h\nu$ $\longrightarrow$ C3 + H2     1.9 $\times$ 10-6 Moses (2000, pers. comm.)
$\dagger $ $\rm C_3$ + $h\nu$ $\longrightarrow$ $\rm C_2$ + C     2.00 $\times$ 10-5 Helbert [this work]
$\rm C_3$ + $h\nu$ $\longrightarrow$ $\rm C_2$ + C     1.00 $\times$ 10-4 (Huebner et al. 1992)
CH4 + $h\nu$ $\longrightarrow$ CH3 + H     2.64 $\times$ 10-7 (Huebner et al. 1992)
CH4 + e $\longrightarrow$ CH3 + H + e 9.43 $\times$ 10-10 (Schmidt et al. 1988)
CH4 + $h\nu$ $\longrightarrow$ CH2 + H2     5.44 $\times$ 10-6 (Huebner et al. 1992)
CH4 + $h\nu$ $\longrightarrow$ CH2 + H + H 2.14 $\times$ 10-6 (Huebner et al. 1992)
CH4 + $h\nu$ $\longrightarrow$ CH + H2 + H 6.39 $\times$ 10-7 (Huebner et al. 1992)
CH2 + $h\nu$ $\longrightarrow$ CH + H     2.00 $\times$ 10-5 (Huebner et al. 1992)
CH + $h\nu$ $\longrightarrow$ C + H     4.16 $\times$ 10-3 (Huebner et al. 1992)
CH3CN + $h\nu$ $\longrightarrow$ CH3 + CN     5.00 $\times$ 10-5 (Huebner et al. 1992)
CH3CN + e $\longrightarrow$ CH3 + CN + e 3.80 $\times$ 10-8 (Schmidt et al. 1988)


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Article Contents
1 Introduction
2 The coma chemistry model
3 Coma profiles used for the analysis
4 The chemistry of possible C2 and C3 parents
5 The main chemical reaction network for the formation of C2 and C3
6 Model input: the nucleus - properties and composition
7 Deriving the production rates
8 Production rates for C2H2, C2H6 and C3H4
9 Error discussion
10 Abundance ratios relative to water and carbon monoxide
11 Abundance ratios relative to acetylene
12 Clues on the formation region of comet Hale-Bopp
13 Summary
References
Online Material
List of tables
List of figures