Dissociative excitation of H/sub 2/, HD, and D/sub 2/ by electron impact. [100 eV electrons]

Journal Article · Thu Sep 01 04:00:00 EDT 1977 · Phys. Rev., A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.16.991· OSTI ID:7297799

Carnahan, B L; Zipf, E C

Time-of-flight techniques have been used to investigate the electron-impact dissociation of H/sub 2/, HD, and D/sub 2/ in order to determine the effect of isotopic mass variation in the target molecule on the dissociative excitation process. At incident electron energies near 100 eV, the time-of-flight spectrum produced from each molecule was found to consist of atoms in the metastable 2s state and in high-lying, long-lived Rydberg levels. The individual time-of-flight distributions, kinetic-energy spectra, and relative differential cross sections for these two species resulting from each molecule have been measured. In several instances these results were found to vary significantly between the three isotopic forms. In particular, the kinetic-energy spectrum of the Rydberg atoms produced from dissociative excitation of H/sub 2/ was notably dissimilar in shape from the corresponding distributions produced from HD and D/sub 2/. Also the 2s and Rydberg production cross sections differed between the three molecules, being less in both cases for HD and D/sub 2/ than for H/sub 2/. In the dissociation of the heteronuclear HD molecule, it was found that the ratio of fast H(2s) atoms to D(2s) atoms was about 1 to 1, while the same ratio comparing the Rydberg atoms was nearly 2 to 1. These differences indicate the influence of the mass variation on the position of the Franck-Condon region in the production of 2s atoms and on the competition between autoionization and dissociation in the formation of Rydberg fragments.

• Research Organization: Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
• OSTI ID: 7297799
• Journal Information: Phys. Rev., A; (United States), Journal Name: Phys. Rev., A; (United States) Vol. 16:3; ISSN PLRAA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
COLLISIONS
CRYOGENIC FLUIDS
DEUTERIDES
DEUTERIUM
DEUTERIUM COMPOUNDS
DISSOCIATION
ELECTRON COLLISIONS
ELECTRON-MOLECULE COLLISIONS
ELEMENTS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EV RANGE
EV RANGE 10-100
EXCITATION
FLUIDS
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN DEUTERIDE
HYDROGEN ISOTOPES
ISOTOPES
LIGHT NUCLEI
MOLECULE COLLISIONS
NONMETALS
NUCLEI
ODD-ODD NUCLEI
STABLE ISOTOPES
TIME-OF-FLIGHT METHOD