CLASSICAL DESCRIPTION OF IONIZATION IN HE2++H COLLISIONS

We report a study on electronic distributions obtained from a CTMC tre atment of the He2+ + H reaction, which may be used as criteria to impr ove the quality of pseudostates within the framework of close-coupling molecular methods. By using the concept of molecular energy of classi cal electrons, an analysis of the mechanism at intermediate energies c onfirms that at low nuclear velocities a sizeable part of the ionizing cloud could be transiently described by bound molecular wavefunctions , at small internuclear distances. However, the description of the ion ization process is incomplete and worsens considerably at velocities l arger than the maximum of the ionization cross section. Hence, pseudos tates are indispensable for representing the evolution of the ionizing cloud, for the whole energy range. The dominant mechanisms in the cla ssical description of ionization are illustrated at velocities close t o the maximum of the cross section. The so-called saddle-point ionizat ion mechanism is seen to correspond to the threshold behaviour of the so-called soft electrons in high-energy treatments. From a study of ou r data, some desirable (and unusual) general properties of the pseudos tates are obtained.