Penning ionization of alkali metals by metastable helium and neon
The rate coefficients for Penning ionization of the alkali metals sodium, potassium, rubidium, and cesium by the 2/sup 3/S/sub 1/ metastable state of helium and of rubidium and cesium by the 3/sup 3/P/sub 1/ metastable state of neon were measured in a stationary afterglow using optical absorption to monitor the metastable atom population. The cross sections for these reactions were obtained under the assumption that the cross section is velocity independent for thermal velocities. The results for helium suggest that collisions in which the metastable energy is near a core-excited state of the alkali (a bound state within the continuum) are more efficient in ionizing the alkali. Since the neon metastable level lies within the core-excited spectrum of both rubidium and cesium, the neon results do not verify or refute this suggestion. For 2/sup 3/S/sub 1/ helium, the measured rate coefficients in units of 10/sup -/exclamation) cm/sup 3/s/sup -1/ are 4.5 +/- 0.9 for cesium, 12.0 +/- 2.4 for rubidium, 7.7 +/- 1.5 for potassium, and 4.5 +/- 0.9 for sodium. The corresponding cross sections in units of 10/sup -16/ cm/sup 2/ are 34 +/- 7 for cesium, 93 +/- 18 for rubidium, 55 +/- 10 for potassium, and 33 +/- 6 for sodium. For 3/sup 3/P/sub 1/ neon, the rate coefficients in units of 10/sup -10/ cm/sup 3/s/sup -1/ are 1.5 +/- 0.3 for cesium and 2.8 +/- 0.6 for rubidium with cross sections in units of 10/sup -16/ cm/sup 2/ of 24 +/- 5 for cesium and 43 +/- 9 for rubidium. The alkali number of density ranged up to 10/sup 12/cm/sup -3/. The helium pressure was about 10 Torr and that of neon about 1 Torr.
- Research Organization:
- North Carolina State Univ., Raleigh (USA)
- OSTI ID:
- 5072685
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CESIUM
ATOM-ATOM COLLISIONS
HELIUM
NEON
POTASSIUM
RUBIDIUM
SODIUM
AFTERGLOW
CROSS SECTIONS
IONIZATION
LOW PRESSURE
METASTABLE STATES
PENNING EFFECT
VELOCITY
ALKALI METALS
ATOM COLLISIONS
COLLISIONS
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FLUIDS
GASES
METALS
NONMETALS
RARE GASES
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena