Ion cyclotron resonance studies of endothermic reactions of UF$sup -$$sub 6$ generated by surface ionization

Journal Article · Sun Feb 01 04:00:00 EST 1976 · J. Chem. Phys., v. 64, no. 3, pp. 929-935

OSTI ID:4077100

Beauchamp, J L

Ion cyclotron resonance spectroscopy is used to investigate endothermic reactions of UF$sup -$$sub 6$. At temperatures below those required for electron emission, UF$sup -$$sub 6$ is formed by negative surface ionization on a directly heated rhenium filament. The reactant ion is accelerated to a known energy and traverses the source region of the ICR cell in the direction of the magnetic field. Slow products from reactive and nonreactive encounters are confined in the trapping well and detected in the usual manner. The formation of UF$sup - $$sub 7$, UF$sup -$$sub 6$, UF$sup -$$sub 5$, and UF$sup -$$sub 3$ from the reaction of UF$sup -$$sub 6$ with UF$sub 6$ is studied over the energy range 0-- 40 eV in the center of mass. The cross section for UF$sup -$$sub 7$ formation exhibits a threshold at a relative kinetic energy of 2.7 eV. Reaction of UF$sup - $$sub 6$ with BF$sub 3$ leads to formation of BF$sup -$$sub 4$ with a threshold of 1.6 eV in the center of mass. From these thresholds, E.A.(UF$sub 6$) =4.9+- 0.5 eV is deduced and the bond dissociation energies D (UF$sub 5$--F$sup -$) =108+-6 kcal/mole and D (UF$sub 6$--F$sup -$) =46+-10 kcal/mole are calculated. The endothermic reaction of UF$sup -$$sub 6$ with SF$sub 6$ to produce SF$sup - $$sub 6$ is also investigated, the cross section for the process exhibiting a gradual onset at approx.7.5 eV, considerably above the thermodynamic threshold. The experimental techniques for using ion cyclotron resonance spectroscopy to study endothermic reactions of positive and negative ions formed by surface ionization are considered in detail. (AIP)

• Research Organization: Contribution No. 5164 from the Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125
• NSA Number: NSA-33-022829
• OSTI ID: 4077100
• Journal Information: J. Chem. Phys., v. 64, no. 3, pp. 929-935, Journal Name: J. Chem. Phys., v. 64, no. 3, pp. 929-935; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

*URANIUM HEXAFLUORIDE-- CHEMICAL REACTIONS
400702* --Chemistry--Radiochemistry & Nuclear Chemistry-- Properties of Radioactive Materials
AFFINITY
CYCLOTRON RESONANCE
DISSOCIATION HEAT
IONIZATION
N40420* --Chemistry--Radiochemistry & Nuclear Chemistry-- Properties of Radioactive Materials