抄録
A laser long-path absorption system was developed by using an infrared Raman-shifter pumped by a tunable dye laser. The spectrum of carbon dioxide in the 2-μm region was mea-sured with the system in an open path with a round-trip path length of 1 km. The concentration of CO2 was determined by fitting a theoretical spectrum to the measured spectrum by the least-squares method. The concentration obtained is consistent very well with the data measured with a non-disperse infrared analyzer. The statistical error in the concentration determined by the least-squares method was investigated theoretically. It is shown that the error in the concentra-tion can be estimated from the noise in the spectrum data by an analytical equation. The statis-tical error in the CO2 concentration measured with the present system is estimated to be 0.8 per-cent for a single wavelength scan measurement.
