The theoretical prediction of intensity distribution in the spectra of many diatomic molecules which are of interest in astrophysics is necessary for an understanding of the physicochemical conditions of the emitting sources. The intensity distribution of various bands in any band system is mainly governed by the Franck-Condon factors.
The transition probability parameters are required for diagnostic applications in astrophysics and allied subjects. The Franck-Condon (FC) factors and r-centroids are important for determining the variation of electronic transition moment with internuclear separation (Rajamanickam 1985; Rajamanickam et al. 1993).
The SiD molecule is located in sun spots whereas SiF and SiN molecules are found in M-type stars (Nicholls 1977).
There has been no report on the FC factors and r-centroids for the band
systems 
of SiD and
of SiF, to our best knowledge, in the literature. In the case of 
of SiN only partial array of Franck-Condon factors
and r-centroids are available (Joshi et al. 1981). Keeping
in view of the above facts, we have carried out the calculation of
Franck-Condon factors and r-centroids for these systems of astrophysical
molecules SiD, SiF and SiN by a more accurate numerical integration
procedure using a suitable potential and the complete array of FC factors
and r-centroids have been presented.