Abstract
A semiquantal theory is applied to the examination of the excitation and ionization produced by the impact between two hydrogen atoms with incident energies E in the range 0.2<or=E<or=2000 keV. Simultaneous transitions in both the target and the projectile atoms are explicitly acknowledged. The cross sections calculated from the simple semiquantal formulas exhibit remarkable harmony with previous quantal calculations. Also, in certain cases, the velocity distribution of the orbital electron can be neglected and the hydrogen-hydrogen excitation cross sections reduce to simple algebraic expressions while the ionization cross sections involve the numerical evaluation of a one-dimensional integral only.