The FC factors indicate that the 
sequence bands are most
intense followed by 
sequence for the 
system of
SiD. The sequence difference for this system is found to be constant and is
about 0.035 Å.
In the case of 
system of SiF, the FC factors indicate that the
(0, 0) band is more intense followed by the sequence
bands. The sequence difference vary between 0.002 Å to
0.012 Å but the sequence difference is found to be
constant and is about 0.009 Å.
In the case of 
system of SiN, Joshi et al. (1981)
have reported FC factors for (0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1),
(1, 2), (2, 0), (2, 1) and (3, 0) bands and r-centroid for (0, 0),
(0, 1), (1, 0), (1, 1), (2, 0), (2, 1), (2, 2),
(3, 0), (3, 1), (3, 2) and
(3, 3) bands. They have used the approximate analytical method proposed by
Fraser & Jarmain (1953). However Bredohl et al.
(1976) have observed experimentally the following 19 bands (8, 1),
(7, 1), (6, 1), (5, 1), (4, 1), (3, 1), (5, 2), (4, 2), (3, 2), (2, 2),
(4, 3), (3, 3), (4, 5), (4, 8), (1, 6), (4, 9), (1, 7), (2, 8), (2, 9).
In the present study the complete array of FC factors and r-centroids have been presented and the calculations are carried out by the most accurate numerical integration procedure.
The sequence difference for this system vary between
0.001 Å to 0.01 Å and the sequence difference vary
between 0.04 Å to 0.128 Å.