Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1997-03-27
1999-07-27
Hannaher, Constantine
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
G01N 2135
Patent
active
059294426
ABSTRACT:
The light absorption spectrum of carbon isotopes .sup.12 CO.sub.2 and .sup.13 CO.sub.2 is measured highly accurately within a short period of time to determine a carbon isotopic abundance ratio highly accurately and reliably. Laser light emitted from a laser diode, which has been slightly modulated with a frequency f and swept in wavelength, passes through a specimen cell and is applied to a photodetector, which produces an electric signal converted from the detected laser light. 2f components of .sup.12 CO.sub.2 and .sup.13 CO.sub.2 of the light absorption spectrum are detected by a lock-in amplifier, and 3f components of .sup.12 CO.sub.2 and .sup.13 CO.sub.2 of the light absorption spectrum are detected by a lock-in amplifier. Spectral intensities of .sup.12 CO.sub.2 and .sup.13 CO.sub.2, which correspond to zero-cross points of the 3f components, are determined from peak values at three points of each of the 2f components, and a carbon isotopic abundance ratio of .sup.12 CO.sub.2 and .sup.13 CO.sub.2 is determined from a ratio of the spectral intensities.
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Hannaher Constantine
Japan Radio Co. Ltd.
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