Collisional depolarization of the lines of complex atoms/ions by neutral hydrogen

We have developed a new semi-classical method for calculating the depolarization and polarization transfer rates of spectral lines of neutral and ionised atoms by collisions with atomic hydrogen (Derouich et al. 2003a, A&A, 404, 763; 2003b, A&A, 409, 369; 2004a, A&A, 414, 369; 2004b, A&A, 426, 707). Up to now, our depolarization rate calculations have been limited to simple atoms. In the present paper, we extend our theory to more complex atoms and we apply our new results to provide the first calculations associated with the upper levels of multiplet 145 of neutral titanium Ti I which constitutes a remarkable example of the second solar spectrum (Manso Sainz & Landi Degl'Innocenti 2002, A&A, 394, 1093).