Alignment effects in the dissociation of H₂⁺ in collisions with laser-excited sodium atoms

Alignment effects are reported for the dissociation of H₂⁺ in collisions with laser-excited sodium in the laboratory collision energy range 600-2400 eV. Measurement of coincidences between H⁺ and H for different laser polarizations enables a straightforward analysis of the experimental results and reduces the number of possible dissociation mechanisms when compared with measurements in which only protons are detected. A mechanism involving autoionization of high-lying Rydberg states of H₂ is proposed as one possible mechanism for the production of protons with very low kinetic energies.