Context. Within shocked regions of the interstellar medium and circumstellar environment of AGB stars the proper modelling of SiO line emission through non-LTE radiative transfer calculations requires accurate values of collisional rate coefficients. Aims. The present study focuses on the transitions among the rotational levels of the SiO molecule in its ground vibrational state induced by collision with He. The H 2 molecule being the main colliding partner for the astrophysical regions of interest, the collisional process between SiO and para-H 2 ( j = 0) is also investigated in an approximated way. Methods. A new 2D SiO-He potential energy surface is computed by means of highly correlated ab initio calculations. Collisional rate coefficients corresponding to the pure rotational (de)excitation of SiO by collision with He are obtained from close-coupling quantum scattering calculations of inelastic cross sections. The SiO-He potential energy surface is also employed to compute rate coefficients for the rotational (de)excitation of SiO by collision with para-H 2 ( j = 0). Results. Rate coefficients for rotational levels up to j = 26 and kinetic temperatures in the range 10-300 K are obtained for the SiO-He colliding system. The large asymmetry of the SiO-He potential energy surface induces a propensity rule that favours odd ∆ j transitions over even ∆ j. The estimated values of the SiO-para-H 2 ( j = 0) rate coefficients are compared with those of Turner et al. (1992) for the twenty first rotational levels. As a result of significant differences between the SiO-He interaction potentials employed in the two studies, the rate coefficients are found to differ by a factor 2.5-5 for the main rotational transitions, whatever the temperature range.

The BASECOL2012 database is a repository of collisional data and a web service within the Virtual Atomic and Molecular Data Centre (VAMDC, http://www.vamdc.eu). It contains rate coefficients for the collisional excitation of rotational, ro-vibrational, vibrational, fine, and hyperfine levels of molecules by atoms, molecules, and electrons, as well as fine-structure excitation of some atoms that are relevant to interstellar and circumstellar astrophysical applications. Submissions of new published collisional rate coefficients sets are welcome, and they will be critically evaluated before inclusion in the database. In addition, BASECOL2012 provides spectroscopic data queried dynamically from various spectroscopic databases using the VAMDC technology. These spectroscopic data are conveniently matched to the in-house collisional excitation rate coefficients using the SPECTCOL sofware package (http:// vamdc.eu/software), and the combined sets of data can be downloaded from the BASECOL2012 website. As a partner of the VAMDC, BASECOL2012 is accessible from the general VAMDC portal (http://portal.vamdc.eu) and from user tools such as SPECTCOL.