Ionizing collisions of He( n sup 1 P ) atoms in a low-Rydberg state with SF sub 6 and NO sub 2 electron-attaching molecules
- Service de Physique des Atomes et des Surfaces, Centre d'Etudes Nucleaires de Saclay, 91191 Gif-sur-Yvette CEDEX (France)
The ionization of He atoms, prepared in a well-defined ({ital n}=14) {sup 1}{ital P} Rydberg state, in collisions with electron-attaching molecules like SF{sub 6} and NO{sub 2}, is studied in a crossed-beam experiment at thermal energies. The ionization cross section is observed to be large for SF{sub 6}, reaching 4.2{times}10{sup {minus}13} cm{sup 2}, and to be smaller for NO{sub 2}, close to 10{sup {minus}15} cm{sup 2}. The dependence of these two cross sections on the relative velocity of the reactants exhibits a characteristic behavior with a saturation at low velocities, a dependence that is completely different from that obtained with polar molecules. The observation of such a dependence for NO{sub 2} indicates that, for this molecule, the reaction product is an ion pair, as for SF{sub 6}, and that ionization is not due to rotational energy transfer even though NO{sub 2} has a dipole moment. This dependence cannot be explained by the free-electron model'' usually used in Rydberg-atom--molecule collisions; it clearly shows that the interaction of the molecule with the ion core cannot be neglected.
- OSTI ID:
- 6416183
- Journal Information:
- Physical Review, A (General Physics); (USA), Vol. 42:1; ISSN 0556-2791
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HELIUM
ATOM-MOLECULE COLLISIONS
NITROGEN DIOXIDE
SULFUR FLUORIDES
BEAM-BEAM INTERACTIONS
ELECTRONEGATIVITY
ION PAIRS
IONIZATION
RYDBERG STATES
ATOM COLLISIONS
BEAM DYNAMICS
CHALCOGENIDES
COLLISIONS
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FLUIDS
FLUORIDES
FLUORINE COMPOUNDS
GASES
HALIDES
HALOGEN COMPOUNDS
MOLECULE COLLISIONS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
OXIDES
OXYGEN COMPOUNDS
RARE GASES
SULFUR COMPOUNDS
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena