Simultaneous monitoring of ³²S, ³³S and ³⁴S isotopes of H₂S using cavity ring-down spectroscopy with a mid-infrared external-cavity quantum cascade laser

Abstract

Monitoring three stable isotopes of H2S using a QCL based CRDS technique.

Gas-Phase Isotopic Fractionation Study of Singly and Doubly Deuterated Isotopologues of Water in the H–D Exchange Reaction by Cavity Ring-Down Spectroscopy

“…A substantial access to the mid-IR region is provided by quantum cascade lasers (QCLs), which enable the high-resolution determination of fine rotational–vibrational features of molecules due to their extremely narrow line width (∼0.0003 cm –1 ). − Moreover, CRDS also provides direct and quantitative assessment of isotope-selective molecular species in the gaseous phase. ,− But isotopic fractionations among singly and doubly deuterated species of water, D 2 16 O, HD 16 O, HD 17 O, and HD 18 O, in the H–D exchange reaction are still largely unknown, and there has been no clear experimental evidence so far in the literature. Therefore, a quantitative analysis of the high-resolution spectral features of D-enriched isotopologues of water exploiting the QCL coupled with CRDS technique would provide a new picture of isotopic fractionation chemistry in the gas phase.…”

Cavity Ring-Down Spectroscopy: Recent Technological Advancements, Techniques, and Applications

“…The group of M. Pradhan developed three independent cw-CRDS systems coupled with three external-cavity (EC) QCLs operating in the mid-IR spectral regions at around 5.2 μm, 6.2 μm, and 7.8 μm for spectroscopic investigations and trace sensing of several molecules like NO, , OCS, , NH 3 , CH 4 , N 2 O, C 2 H 2 , H 2 S, and D 2 O and their isotopologues. , The group subsequently exploited the cw-CRDS technique for the spectroscopic study of long-chain hydrocarbons like 1,3 butadiene where experimental results were simultaneously compared with the theoretical calculations from Gaussian 16 and PGOPHER simulation . In a recent study, Pal et al reported the natural abundances of 32 S, 33 S, and 34 S isotopes in a sulfur compound, Na 2 S, which was reacted with HCl to form the gaseous H 2 S to be eventually measured by the cw-CRDS system probing the transition lines of three sulfur isotopes in the spectral region of 7.8 μm. However, Maithani et al from the same group provided the first experimental measurements of the H-D exchange process by simultaneously measuring monodeuterated (HDO) and doubly deuterated (D 2 O) isotopes in the H 2 O–D 2 O reaction medium.…”

“…In a recent study by Yuan et al, 180 a compact CRDS system for real-time in situ measurement of dissolved CH 4 in seawater was demonstrated and subsequently field tested in an actual underwater environment with a detection sensitivity of 0.4 ppm with 4 min of data averaging. The measurement accuracy of the prototype CRDS system was further validated in 191 and D 2 O 14 and their isotopologues. 188,192 The group subsequently exploited the cw-CRDS technique for the spectroscopic study of long-chain hydrocarbons like 1,3 butadiene where experimental results were simultaneously compared with the theoretical calculations from Gaussian 16 and PGOPHER simulation.…”

“…188,192 The group subsequently exploited the cw-CRDS technique for the spectroscopic study of long-chain hydrocarbons like 1,3 butadiene where experimental results were simultaneously compared with the theoretical calculations from Gaussian 16 and PGOPHER simulation. 193 In a recent study, 191 Pal et al reported the natural abundances of 32 S, 33 S, and 34 S isotopes in a sulfur compound, Na 2 S, which was reacted with HCl to form the gaseous H 2 S to be eventually measured by the cw-CRDS system probing the transition lines of three sulfur isotopes in the spectral region of 7.8 μm. However, Maithani et al 14 In a study by Taha et al, 194 a new methodology in combination with the CRDS technique was demonstrated for the detection of explosive compound, triacetone triperoxide (TATP).…”

Parts-per-billion-level detection of hydrogen sulfide based on doubly resonant photoacoustic spectroscopy with line-locking

“…The absorption path length can be further increased to several kilometers by a high-finesse optical cavity [22] , [23] , [24] . Off-axis integrated cavity output spectroscopy (ICOS) [23] and cavity ring-down spectroscopy (CRDS), for instance, have contributed to breakthroughs in H 2 S detection, particularly a detection limit of 20 ppb [25] . However, the technical limitations, such as limited dynamic range due to the intracavity absorption [26] , etalon effects superposed on photodetectors [27] , and bulky chamber with a large gas consumption, may restrict its wide applications out of laboratory.…”