Collisional excitation of thioformaldehyde and of Silylidene

For analysis of spectrum of a molecule in the interstellar medium, radiative and collisional transition probabilities for rotational transitions in the molecule are required. We have calculated collisional rate coefficients for rotational transitions in ortho and para thioformaldehyde (H2CS), and in ortho and para Silylidene (H2CSi) due to collisions with He atom for kinetic temperatures 10, 20, 30, 40 and 50 K, following the procedure discussed in our earlier work. The accuracy of collisional rate coefficients may be within a factor of 2.