Time-resolved production and detection of reactive atoms
Cesium iodide in the presence of a buffer gas was dissociated with a pulsed ultraviolet laser, which will be referred to as the source laser. This created a population of atoms at a well defined time and in a compact, well defined volume. A second pulsed laser, with a beam that completely surrounded that of the first, photoionized the cesium after a known time delay. This laser will be referred to as the detector laser. It was determined that for short time delays, all of the cesium atoms were easily ionized. When focused, the source laser generated an extremely intense fluence. By accounting for the beam intensity profile it was shown that all of the molecules in the central portion of the beam can be dissociated and detected. Besides proving the feasibility of single-molecule detection, this enabled a determination of the absolute photodissociation cross section as a function of wavelength. Initial studies of the time decay of the cesium signal at low argon pressures indicated a non-exponential decay. This was consistent with a diffusion mechanism transporting cesium atoms out of the laser beam. Therefore, it was desired to conduct further experiments using a tightly focused source beam, passing along the axis of the detector beam. The theoretical behavior of this simple geometry accounting for diffusion and reaction is easily calculated. A diffusion coefficient can then be extracted by data fitting. If reactive decay is due to impurities constituting a fixed percentage of the buffer gas, then two-body reaction rates will scale linearly with pressure and three-body reaction rates will scale quadratically. Also, the diffusion coefficient will scale inversely with pressure. At low pressures it is conceivable that decay due to diffusion would be sufficiently rapid that all other processes can be neglected. Extraction of a diffusion coefficient would then be quite direct. Finally, study of the reaction of cesium and oxygen was undertaken.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- US Energy Research and Development Administration (ERDA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5274404
- Report Number(s):
- ORNL/TM-6014; TRN: 78-002929
- Resource Relation:
- Other Information: Thesis. Submitted by L.W. Grossman
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CESIUM
ATOM-ATOM COLLISIONS
CESIUM IODIDES
PHOTOIONIZATION
OXYGEN
ARGON
CHEMICAL REACTIONS
LASER RADIATION
ALKALI METAL COMPOUNDS
ALKALI METALS
ATOM COLLISIONS
CESIUM COMPOUNDS
COLLISIONS
CRYOGENIC FLUIDS
ELECTROMAGNETIC RADIATION
ELEMENTS
FLUIDS
HALIDES
HALOGEN COMPOUNDS
INORGANIC PHOSPHORS
IODIDES
IODINE COMPOUNDS
IONIZATION
METALS
NONMETALS
PHOSPHORS
RADIATIONS
RARE GASES
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena