Collision-induced ion-pair formation of the thallium halides TlF and Tl/sub 2/F/sub 2/

Journal Article · Sat Oct 01 00:00:00 EDT 1977 · J. Chem. Phys.; (United States)

OSTI ID:7090773

Parks, E K; Kuhry, J G; Wexler, S

Absolute cross sections have been determined for collision-induced ion-pair formation (polar dissociation) of TlF and Tl/sub 2/F/sub 2/ from collisions with Xe and Kr atoms. A crossed-beam method was used in which the Xe or Kr atoms were aerodynamically accelerated to energies up to 17 eV (in the laboratory frame). Time-of-flight mass spectrometry permitted the determination of partial cross sections for each positive and negative ion channel in the collision. With new values of the heats and entropies of formation of Tl/sub 2/Cl/sub 2/, Tl/sub 2/Br/sub 2/, and Tl/sub 2/I/sub 2/ the absolute cross sections for the previously reported reactions of the dimers Xe(Kr)+Tl/sub 2/X/sub 2/..-->..Xe(Kr)+Tl/sub 2/X/sup +/+X/sup -/ have been recalculated. The threshold behaviors of these reactions have also been analyzed in terms of the above power law, giving values of the power n in the range 2.1--2.7. Model calculations have been performed to determine bond energies of the (Tl--X--Tl)/sup +/ and (X--Tl--X)/sup -/ ions, which were used to determine theoretical thresholds for the formation of these ions. The difference between the experimental and theoretical thresholds then gives the internal excitation of the molecular ions at threshold (assuming the inert gas atom carries away negligible energy). Tl/sub 2/F/sup +/, in particular, is formed at threshold with considerable internal excitation (approx.1.8 eV). The low cross sections for both TlF and Tl/sub 2/F/sub 2/ and the high internal excitation of Tl/sub 2/F/sup +/ at threshold are consistent with a collision model in which only very dynamically constrained collisions result in the extraction of the light F/sup -/ ion from either TlF or Tl/sub 2/F/sub 2/.

• Research Organization: Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439
• OSTI ID: 7090773
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 67:7; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
BEAMS
COLLIDING BEAMS
COLLISIONS
CROSS SECTIONS
ELEMENTS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
ION PAIRS
KRYPTON
MOLECULAR BEAMS
MOLECULE COLLISIONS
NONMETALS
RARE GASES
THALLIUM COMPOUNDS
THALLIUM FLUORIDES
TIME-OF-FLIGHT METHOD
XENON