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4 Results

The calculations are made for the upward transitions $J \tau \rightarrow
J' {\tau'}$. For ortho-C3H2, we accounted for 47 energy levels given in Table 1A. The calculations are done for the kinetic temperatures 30, 60, 90, and 120 K, and the results are presented in Tables 3A, 3B, 3C, and 3D, respectively. For para-C3H2, we accounted for 48 energy levels given in Table 1B. For this case also, the calculations are done for the kinetic temperatures 30, 60, 90, and 120 K, and the results are presented in Tables 4A, 4B, 4C, and 4D, respectively. For ortho-SiC2, we accounted for 40 energy levels given in Table 2. The calculations are done for the kinetic temperatures 25, 50, 75, 100, and 125 K, and the results are presented in Tables 5A, 5B, 5C, 5D, and 5E, respectively. The rate coefficient for the corresponding downward transition $J' \tau' \rightarrow J\tau$ can easily be calculated with the help of the detailed equilibrium equation


$\displaystyle C(J' \tau' \rightarrow J\tau) = \frac{2J + 1}{2J' + 1}\mbox{exp}\left[
\frac{hc[E(J' \tau') -E(J \tau)]}{kT} \right]$      
$\displaystyle C(J\tau \rightarrow J' \tau')$      

where the energy E of the energy level is in cm-1. The Tables 3A, 3B, 3C, 3D, 4A, 4B, 4C, 4D, 5A, 5B, 5C, 5D and 5E are available only in electronic form via anonymous ftp. However, a part of the Table 3A is given in printed form in order to have the information about the content of the tables. There we have given (i) transition, (ii) collisional rate coefficient (in cm3 s-1), (iii) lower energy level number(l) of the transition (according to the table of wave-functions), and (iv) upper energy level number(u) of the transition.

Acknowledgements
This work was done during the visit of Prof. S. Chandra under the scientific exchange program between the INSA, New Delhi (India) and the DFG, Bonn (Germany). Prof. Chandra is thankful to Prof. J.M. Waghmare, Vice-Chancellor of the S.R.T.M. University, Nanded for his encouragements.

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