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

Abstract

An infrared absorption spectrometer has been constructed to measure the stable isotopic composition of atmospheric methane samples. The spectrometer employs periodically poled lithium niobate to generate 15 W of tunable difference-frequency radiation from two near-infrared diode lasers that probe the 3 rotational-vibrational band of methane at 3.4 m. To enhance the signal, methane is extracted from 25 l of air by use of a cryogenic chromatographic column and is expanded into the multipass cell for analysis. A measurement precision of 12‰ is demonstrated for both ␦ 13 C and ␦D.

Interband cascade laser–based sensor for ambient CH₄

“…Baer et al 13 also developed a near-IR TDL sensor for CH 4 operating at 1.67 μm in combination with ICOS, which provides ∼2100 m of optical path, to achieve a sensitivity of 1 ppbv for 1-s acquisition. There are several current efforts 14,15 to develop spectrometers to measure the 12 CH 4 / 13 CH 4 ratio.…”

A TC/WMS-TDLAS mid-infrared detection method for ultra-low concentration carbon isotope methane

“…12 CH 4 and 13 CH 4 are different products of thermal cracking or microbial degradation of organic matter. 1,2 The detection of 12 CH 4 and 13 CH 4 concentrations is commonly used to analyze the origin of carbon or monitor the carbon changes in the formation and environment, for example, it has been applied to oil and natural gas exploration, [3][4][5] coal bed methane analysis, [6][7][8][9] atmospheric environmental testing and biology.…”

Hydrogen/Deuterium (H/D) Exchange Catalysis in Alkanes

“…This area has been the subject of several reviews. − Other systems were also discovered that could carry out H/D exchange, including metal oxides (especially dehydrated aluminas, detailed below), superacids, , and molecular organometallic complexes. − This research has implications for hydrocarbon conversion to more useful products and is therefore of interest to the catalysis community. In addition to fundamental studies of catalysis, other research areas have exploited H/D exchange, and some examples are labeling studies for polymer characterization by neutron scattering techniques, − fundamental studies on equilibrium isotope effects in organometallic compounds, − kinetic and equilibrium studies on the geochemical isotopic distribution of natural occurring hydrocarbons, − and applications of H/D exchange for small molecule synthesis and pharmaceuticals. − This article serves to review the literature on H/D exchange in alkanes, starting from its initial discovery in 1935. A brief background on isotope effects is followed by the H/D exchange studies and is broken down into two classes: metal catalysts and metal oxide catalysts.…”