Rotational excitation of HD+ by electron and positron impact

The rotational excitation cross sections for Δj=+-1 and +-2 transitions for HD+ by electron and positron impact have been calculated by the semi-classical first-order time-dependent perturbation theory. The trajectory is assumed to be determined by the spherical Coulomb interaction from the dipole moment, quadrupole moment and anisotropy of polar-izability of HD+. The energy ranges covered are 0.04 eV to 5 eV for electron-HD+ and 0.1 eV to 5 eV for positron-HD+ collisions. The effect of penetration of the charge cloud of HD+ is seen to be small for Δj=+-1 transitions and very large for Δj=+-2 transitions. For electron-HD+ collisions the cross section for rotational excitation decreases with the increase of energy. The reverse is the case of positron-HD+ collisions. (author)