INFRARED ABSORPTION BY METHANE ISOTOPES NEAR 2999 CM(-1) - AN ANALYTICAL METHOD USING THE ZEEMAN SPLIT HE-NE LASER LINE AT 2999.24 CM(-1)

摘要

We report the strengths and locations of the absorption lines of CH3D, (CH4)-C-13, and (CH4)-C-12 in the vicinity of the helium-neon laser line at 2999.24 cm(-1). In this region we find intrinsically strong lines of the rare species overlapping, but not precisely coincident with, intrinsically weak lines of the major species. In methane of normal isotopic composition, the lines of all three species have comparable strengths. We show how absorption measurements of the He-Ne laser, with Zeeman splitting, can be used to determine variations of the concentrations of the rare species from standard concentrations at a calculated precision of 0.5 parts per thousand. [References: 29]