Infrared spectroscopic analysis method for gases and device employing the method therein

An infrared spectroscopic analysis method for gases, for analyzing an impurity in a gas to be measured, comprising the steps of:

• measuring absorption intensity by passing light in the infrared region through the gas to be measured, wherein the gas to be measured is analyzed in a low pressure state;
• dissociating clusters formed by molecules of the impurity of the gas to be measured;
• measuring the absorption spectrum for the gas to be measured and the absorption spectrum for the impurity alone by scanning the wavelength of light to be passed through the gas to be measured;
• comparing the absorption spectrum for the gas to be measured and the absorption spectrum for the impurity alone;
• confirming presence of a plurality of absorption peaks associated with the impurity;
• and
• determining the impurity by selecting from this plurality of peaks a strongest peak not experiencing interference from nearby peaks and determining the impurity from an absorption intensity of the strongest peak.

An infrared spectroscopic analysis device, comprising:

• a wavelength tunable diode laser that oscillates infrared region light;
• means for passing light oscillated from the laser through a gas to be measured;
• means for measuring the intensity of the laser light which has passed through the gas to be measured, wherein infrared spectroscopy is used to analyze a gaseous impurity in the gas to be measured;
• means for lowering the pressure of the gas to be measured;
• means for irradiating the gas to be measured with light having a photon energy of 0.5 eV or greater;
• means for branching the light oscillated from the diode laser and passing a first portion of the branched light through the gas to be measured while passing a second portion of the branched light through the gaseous impurity alone;
• means for respectively measuring the absorption spectrum of the light passed through the gas to be measured and the absorption spectrum of the light which passed through the gaseous impurity alone;
• and
• means for comparing the absorption spectrum of the light which passed through the gas to be measured and the absorption spectrum for light which passed through the gaseous impurity alone, recognizing from among the absorption peaks of the absorption spectrum of the light which passed through the gas to be measured the absorption peak for which the absorption wavelength coincides with the absorption peak of the absorption spectrum for the light which passed through the gaseous impurity alone, and detecting the absorption intensity of this absorption peak.