Chemi-ionization reactions in accelerated uranium--O$sub 2$ crossed molecular beams

Journal Article · Thu Jan 01 00:00:00 EST 1976 · J. Chem. Phys., v. 64, no. 1, pp. 306-319

OSTI ID:4083800

Young, C E; Dehmer, P M; Cohen, R B; Pobo, L G; Wexler, S

Chemi-ionization and electron transfer reactions in accelerated uranium- atom--oxygen-molecule collisions have been studied by crossed molecular beam techniques: U+O$sub 2$$Yields$UO$sup +$$sub 2$+e, associative ionization (1); U+O$sub 2$$Yields$UO$sup +$+(O+e), rearrangement (reactive) ionization (2); U+O$sub 2$$Yields$$U$$sup +$+(O$sub 2$+e), electron transfer (3). Cross sections for the three ionization channels were measured as a function of relative collision energy from 0.2 to 60 eV. The thresholds observed for channels (2) and (3), which are closed at thermal energies, are in good agreement with values calculated from thermochemical data. The cross section for associative ionization varied inversely with v/subr/, the relative collision velocity, as predicted for weak autoionizing transitions. With the use of a rough absolute calibration and a 1/v/subr/ extrapolation to lower energies, the UO$sup +$$sub 2$ cross section was found to be in agreement with the previously reported value measured with thermal beams. In the case of rearrangement ionization, the cross section rose rapidly at threshold, peaked near the threshold for the electron transfer process, and then declined with increasing collision energy. The electron transfer cross section increased with a power-law dependence of the excess energy above threshold throughout the range investigated. The maximum absolute cross section measured was 1.4x10$sup -17$ cm$sup 2$. The dynamics of ionization processes (2) and (3) were elucidated from the energy dependences of the cross sections and from measurements of the angular and kinetic energy distributions of the product ions. The results support the conclusion that rearrangement ionization proceeds by a ''spectator-stripping'' mechanism. Both the UO$sup +$ from this reaction and the U$sup +$ from electron transfer are scattered predominantly in the forward direction. (AIP)

• Research Organization: Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439
• NSA Number: NSA-33-021154
• OSTI ID: 4083800
• Journal Information: J. Chem. Phys., v. 64, no. 1, pp. 306-319, Other Information: Orig. Receipt Date: 30-JUN-76
• Country of Publication: United States
• Language: English

Related Subjects

N60400* -Physics (Atomic & Molecular)-Collision Phenomena
640304* -Physics Research-Atomic
Molecular & Chemical Physics-Collision Phenomena
*OXYGEN- ATOM-MOLECULE COLLISIONS
*URANIUM- ATOM-MOLECULE COLLISIONS
ANGULAR DISTRIBUTION
CHARGE EXCHANGE
CHEMICAL REACTIONS
COLLIDING BEAMS
CROSS SECTIONS
ELECTRONS
ENERGY DEPENDENCE
EV RANGE 01-10
EV RANGE 10- 100
IONIZATION
KINETIC ENERGY
MILLI EV RANGE
OXYGEN IONS
REACTION KINETICS
URANIUM IONS
URANIUM OXIDES