Method for measuring concentration of fluorine gas contained in halogen fluoride-containing gas by ultra violet spectroscopy
A method for measuring the concentration of fluorine gas, which includes irradiating a halogen fluoride-containing gas with ultraviolet light in which the ratio (W X /W F ) of the maximum value (W X ) of ultraviolet light intensity in the wavelength region of less than 250 nm with respect to the ultraviolet light intensity (W F ) at a wavelength of 285 nm is 1/10 or less, and measuring the absorbance at a wavelength of 285 nm to obtain the concentration of fluorine gas contained in the halogen fluoride-containing gas.
1. A method for measuring a concentration of fluorine gas, the method comprising:
irradiating a halogen fluoride-containing gas with ultraviolet light in which a ratio (W X /W F ) of a maximum value (W X ) of ultraviolet light intensity in a wavelength region of less than 250 nm with respect to an ultraviolet light intensity (W F ) at a wavelength of 285 nm is 1/10 or less; and
measuring an absorbance at a wavelength of 285 nm to obtain a concentration of fluorine gas contained in the halogen fluoride-containing gas.
2. The method for measuring a concentration of fluorine gas according to claim 1 , wherein
using a means for suppressing irradiation with ultraviolet light of wavelengths of less than 250 nm, the halogen fluoride-containing gas is irradiated with ultraviolet light of wavelengths of not less than 250 nm from a light source.
3. The method for measuring a concentration of fluorine gas according to claim 1 , wherein
the means is to irradiate the ultraviolet light irradiated from the light source to the halogen fluoride-containing gas via a filter that blocks at least 50% of the ultraviolet light with a wavelength of less than 250 nm and transmits at least 90% of the ultraviolet light with a wavelength of 280-290 nm.
4. The method for measuring a concentration of fluorine gas according to claim 1 , wherein
the halogen fluoride is one kind of gas selected from the group consisting of chlorine trifluoride, bromine pentafluoride, iodine heptafluoride, bromine trifluoride, and iodine pentafluoride.
5. The method for measuring a concentration of fluorine gas according to claim 1 , wherein
the halogen fluoride is iodine heptafluoride.
6. The method for measuring a concentration of fluorine gas according to claim 1 , wherein
the halogen fluoride is bromine pentafluoride, and
the maximum value (W X ) of ultraviolet light intensity in the wavelength region of less than 250 nm is a maximum value of ultraviolet light intensity in a wavelength region of less than 225 nm.
7. The method for measuring a concentration of fluorine gas according to claim 1 , wherein
the halogen fluoride is chlorine trifluoride, and
the maximum value (W X ) of ultraviolet light intensity in the wavelength region of less than 250 nm is a maximum value of ultraviolet light intensity in a wavelength region of less than 215 nm.
8. The method for measuring a concentration of fluorine gas according to claim 1 , wherein
an absorption spectrum measured by irradiating a reference gas with the ultraviolet light is subtracted from an absorption spectrum measured by irradiating the halogen fluoride-containing gas with the ultraviolet light, and
the concentration of fluorine gas is obtained from an absorbance at a wavelength of 285 nm of an obtained absorption spectrum.