Radiant energy – Luminophor irradiation
Patent
1977-11-28
1982-01-26
Smith, Alfred E.
Radiant energy
Luminophor irradiation
356311, G01J 158, G01J 330
Patent
active
043130577
ABSTRACT:
An arrangement for detecting low concentrations of atoms. A gaseous sample containing the atoms to be detected is provided and the atoms have a plurality of energy levels with photon inducible transitions between a first energy level and a second level and collision inducible transitions between the second energy level and a third energy level. The atoms undergo spontaneous energy emitting transitions from the third energy level to either the first energy level or to a fourth energy level which is collision coupled to the first energy level. A beam of photons which may be generated, for example, by a laser, having photons with a wave length corresponding to the wave length separation between the first energy level and the second level is provided to irradiate the gaseous sample. A buffer gas is provided in order to collide with the atoms at the second energy level thereby inducing transitions to the third energy level. If a fourth level is utilized, collision with the buffer gas also induces transitions from the fourth level back to the first level. A detection means is provided to monitor the wave length emitted by the atoms in the spontaneous transition from the third energy level to either the first energy level or the fourth energy level. The wave length separation between the first energy level and second energy level is different from the wave length separation between the third energy level and either the first or fourth energy level and therefore detection of the energy emitted from the atoms during transitions from the third energy level to the first energy level or fourth level is at a wave length different from the wave length of the photons utilized to induce transitions between the first energy level and second energy level. The intensity of the beam of photons is selected to provide for saturation of the population distribution at the various energy levels in order to maximize the emission rate even in the presence of ambient gases that may tend to quench the characteristic emissions. Thus, detection can take place for the gaseous sample maintained at, for example, one atmosphere pressure. The signal derived from the detection of the wave length emitted by the atoms during transitions from the third energy level to the first energy level or fourth level is a measure of the atomic density in the gaseous sample.
REFERENCES:
patent: 3566114 (1971-02-01), Brewer
patent: 4019060 (1977-04-01), Woodman
Becker et al., "Fluorescence Determination of Low Formaldehyde Concentrations in Air by Dye Laser Excitation," Applied Optics, vol. 14, No. 2, pp. 310-313, Feb. 1975.
Finkelstein Don
Howell Janice A.
Smith Alfred E.
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