Excitation processes in a Pb-He discharge
Journal Article
·
· J. Appl. Phys.; (United States)
Measurements of the emission from Pb/sup +/ in the afterglow of a pulsed He : Pb discharge in a large-bore tube and of the intensities of Pb/sup +/ and Pb emission lines in a small-bore dc discharge tube have been made to clarify the excitation mechanism of the He : Pb laser. In both He : pure Pb and He : Pb containing a low concentration of Cd to act as a probe, the rate constants for the decay of the Pb/sup +/ and Cd/sup +/ emission lines obtained using the large-bore tube indicated that the only excitation mechanism was thermal charge exchange between /sup 2/S/sub 1/2/He/sup +/ and ground-state Pb atoms. The collision cross section for the He/sup +/-Pb reaction was determined to be 4.0 x 10/sup -/16 cm/sup 2/ from measurements of the variations of the decay rates of the 5608.8-A Pb/sup +/, 4386.4-A Pb/sup +/, and 5378-A Cd/sup +/ emission lines with Pb concentration. The variation of the rate constant of the 4416-A Cd/sup +/ line indicated that the collision cross section for the 2s /sup 3/S/sub 1/ He-Pb Penning ionization is 14.8 x 10/sup -/16 cm/sup 2/. In a small-bore tube, Penning ionization was verified to be the dominant excitation mechanism for the 4245-A Pb/sup +/ emission line but not the 5608-A Pb/sup +/ laser line. The change in the relative importance of the various excitation mechanisms with the discharge-tube diameter, and its ramifications regarding other metal-vapor laser systems, is discussed.
- Research Organization:
- Department of Physics, Western Illinois University, Macomb, Illinois 61455
- OSTI ID:
- 6847087
- Journal Information:
- J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 49:5; ISSN JAPIA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
640304 -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
AFTERGLOW
CHARGE EXCHANGE
COLLISIONS
CROSS SECTIONS
CRYOGENIC FLUIDS
ELECTRIC DISCHARGES
ELEMENTS
EMISSION SPECTRA
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
FLUIDS
GAS LASERS
HELIUM
LASERS
LEAD
METALS
METASTABLE STATES
NONMETALS
PENNING EFFECT
POSITIVE COLUMN
RARE GASES
SPECTRA
420300* -- Engineering-- Lasers-- (-1989)
640304 -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
AFTERGLOW
CHARGE EXCHANGE
COLLISIONS
CROSS SECTIONS
CRYOGENIC FLUIDS
ELECTRIC DISCHARGES
ELEMENTS
EMISSION SPECTRA
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
FLUIDS
GAS LASERS
HELIUM
LASERS
LEAD
METALS
METASTABLE STATES
NONMETALS
PENNING EFFECT
POSITIVE COLUMN
RARE GASES
SPECTRA