Collision induced molecular rotation of SiC4-He for astrophysical implications

To probe the physical conditions in molecular clouds, observations of the rotational transitions of a molecular system are very important. Thus, accurate modelling of the emission spectra of silicon carbides requires the calculation of collision rate coefficients for its systems. We determine here, the collisional rate coefficients for the excitation of SiC4 by He using a new potential energy surface. The state-to-state rate coefficients between the lower levels (j <= 28) are calculated using the coupled-channel and coupled-state methods for temperatures ranging from 5 to 300 K. Finally, we model the excitation of the SiC4 radical in cold molecular clouds and star-forming regions using a radiative transfer model. For this purpose, the new rate coefficients are used to estimate the molecular abundances in interstellar clouds. Therefore, we recommend the use of this new data set in any astrophysical model of SiC4 radical excitation.