Investigations of the Potential Functions of Weakly Bound Diatomic Molecules and Laser-Assisted Excitive Penning Ionization

摘要

Three variations on the Dunham series expansion function of the potential of a diatomic molecule are compared. The differences among these expansions lie in the choice of the expansion variable, lambda. The functional form of these variables are lambda/sub s/ = l-r/sub e//r for the Simon-Parr-Finlan version, lambda/sub T/ - 1-(r/sub e//r)/sup p/ for that of Thakkar, and lambda/sub H/ = 1-exp(-rho(r/r/sub e/-1) for that of Huffaker. A wide selection of molecular systems are examined. It is found that, for potentials in excess of thirty kcal/mole, the Huffaker expansion provides the best description of the three, extrapolating at large internuclear separation to a value within 10% of the true dissociation energy. For potentials that result from the interaction of excited states, all series expansions show poor behavior away from the equilibrium internuclear separation of the molecule. The series representation of the potentials of weakly bound molecules are examined in more detail. The ground states of BeAr exp + , HeNe exp + , NaAr, and Ar sub 2 and the excited states of HeNe+, NaNe, and NaAr are best described by the Thakkar expansion. Finally, the observation of laser-assisted excitive Penning ionization in a flowing afterglow is reported. The reaction Ar( exp 3 P sub 2 ) + Ca + h nu implies Ar + Ca exp + (5p exp 2 P/sub J/) + e exp - occurs when the photon energy, h nu, is approximately equal to the energy difference between the metastable argon and one of the fine structure levels of the ion's doublet. By monitoring the cascade fluorescence of the above reaction and comparing it to the flourescence from the field-free process Ar( exp 3 P sub 2 ) + Ca implies Ar + Ca exp + (4p exp 2 P/sub J/) + e exp - a surprisingly large cross section of 6.7 x 10 exp 3 A exp 2 is estimated. (ERA citation 07:055373)