Third-harmonic generation for photoionization studies
Our group at Oak Ridge National Laboratory (ORNL) has studied resonantly enhanced multiphoton ionization (MPI) of alkali atoms, rare gases, and small molecules using tightly focused dye laser beams (power densities of 10/sup 9/ to 10/sup 11/ W/cm/sup 2/). In the case of alkali atoms, some ionization signals appear as a result of gas density effects (dimers or quasi-collisions) as previously discovered by Collins and his collaborators. These have been termed hybrid-resonances. By contrast, in the case of the rare gases, certain resonance ionization signals disappear with increasing gas density. The disappearance of the ionization signals in the rare gases is due to the interference of excitation of the third-harmonic and fundamental laser beam. At low pressure (10/sup -7/ to 10/sup -5/ torr) we have studied (1) mass spectra, (2) kinetic energy released in ionic fragmentation, and (3) photoelectron kinetic energy spectra using time-of-flight mass analysis and a 160/sup 0/ spherical sector electrostatic energy analyzer. These experiments, combined with two-color dye laser experiments, can often offer an unambiguous and detailed description of the MPI and subsequent fragmentation events. The major part of this talk will be devoted to the production and the use of vacuum ultraviolet (VUV) light from third-harmonic generation (THG) in the rare gases.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 6695367
- Report Number(s):
- CONF-821073-1; ON: DE83001960
- Resource Relation:
- Conference: US/Japan seminar on electron-molecule collsions and photoionization processes, Pasadena, CA, USA, 26 Oct 1982
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
PHOTON-ATOM COLLISIONS
IONIZATION
PHOTON-MOLECULE COLLISIONS
HARMONICS
LASER RADIATION
MASS SPECTROSCOPY
MOLECULES
RARE GASES
ULTRAVIOLET RADIATION
ATOM COLLISIONS
COLLISIONS
ELECTROMAGNETIC RADIATION
ELEMENTS
FLUIDS
GASES
MOLECULE COLLISIONS
NONMETALS
OSCILLATIONS
PHOTON COLLISIONS
RADIATIONS
SPECTROSCOPY
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena