Abstract

We report the strengths and locations of the absorption lines of CH₃D, ¹³CH₄, and ¹²CH₄ 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‰.

© 1996 Optical Society of America

Atmospheric methane measurement instrument using a Zeeman-split He–Ne laser

J. Barry McManus, Paul L. Kebabian, and Charles E. Kolb
Appl. Opt. 28(23) 5016-5023 (1989)

Stable isotopic analysis of atmospheric methane by infrared spectroscopy by use of diode laser difference-frequency generation

Michael E. Trudeau, Pin Chen, Guilherme de Andrade Garcia, Leo W. Hollberg, and Pieter P. Tans
Appl. Opt. 45(17) 4136-4141 (2006)

Diode laser absorption measurements of CH₃Cl and CH₄ near 1.65 µm

Shang-I Chou, Douglas S. Baer, and Ronald K. Hanson
Appl. Opt. 36(15) 3288-3293 (1997)

Measuring methane and its isotopes ¹²CH₄, ¹³CH₄, and CH₃D on the surface of Mars with in situ laser spectroscopy

Christopher R. Webster
Appl. Opt. 44(7) 1226-1235 (2005)

Tunable diode-laser absorption measurements of methane at elevated temperatures

V. Nagali, S. I. Chou, D. S. Baer, R. K. Hanson, and J. Segall
Appl. Opt. 35(21) 4026-4032 (1996)