Sensitive magnetic rotation spectroscopy of the OH free radical fundamental band with a colour centre laser

Pfeiffer, Joann M.; Kirsten, Dagmar; Kalkert, P.; Urban, W.

doi:10.1007/bf00692443

Cited by 31 publications

(10 citation statements)

References 10 publications

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“…Non-optimum spectral line; Signal loss due to beam splitter; low heterodyne efficiency; RF mixer noise *Note: the shot noise Θ SNEA /(Δf) 1/2 is calculated with Eqs. (12) and (13) based on the actual experimental conditions: P 0 = 2.9 mW for Ref [6], P 0 = 60 mW for Ref [7], P 0 = 0.015 mW for Ref [13], and P 0 = 14 mW was used for H-FRS. The detector quantum efficiency of η = 0.5 was assumed in all C-FRS systems, which is a moderate number that should provide a good approximation of the system's fundamental limit.…”

Section: Comparison With Other Frs Systemsmentioning

confidence: 99%

“…Since first reported in the 1980s [1], Faraday rotation spectroscopy (FRS) has been used as a sensitive and selective technique for the detection of gas-phase paramagnetic species such as NO [1][2][3][4][5][6][7], NO 2 [8,9], O 2 [10,11], and OH radicals [12,13]. In the presence of magnetic field, the transition states of the paramagnetic molecules split due to the Zeeman Effect causing magnetic circular birefringence (MCB, a difference in refractive indices for lefthanded (LHCP), and right-handed (RHCP) circularly polarized components) and magnetic circular dichroism (MCD, a difference in absorption coefficients for LHCP and RHCP).…”

Section: Introductionmentioning

confidence: 99%

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Cryogen-free heterodyne-enhanced mid-infrared Faraday rotation spectrometer

2013

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A new detection method for Faraday rotation spectra of paramagnetic molecular species is presented. Near shot-noise limited performance in the mid-infrared is demonstrated using a heterodyne enhanced Faraday rotation spectroscopy (H-FRS) system without any cryogenic cooling. Theoretical analysis is performed to estimate the ultimate sensitivity to polarization rotation for both heterodyne and conventional FRS. Sensing of nitric oxide (NO) has been performed with an H-FRS system based on thermoelectrically cooled 5.24 μm quantum cascade laser (QCL) and a mercury-cadmium-telluride photodetector. The QCL relative intensity noise that dominates at low frequencies is largely avoided by performing the heterodyne detection in radio frequency range. H-FRS exhibits a total noise level of only 3.7 times the fundamental shot noise. The achieved sensitivity to polarization rotation of 1.8 × 10(-8) rad/Hz(1/2) is only 5.6 times higher than the ultimate theoretical sensitivity limit estimated for this system. The path- and bandwidth-normalized NO detection limit of 3.1 ppbv-m/Hz(1/2) was achieved using the R(17/2) transition of NO at 1906.73 cm(-1).

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Section: Comparison With Other Frs Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cryogen-free heterodyne-enhanced mid-infrared Faraday rotation spectrometer

2013

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“…FRS has been used for many years as a very sensitive and selective technique for the spectroscopic investigation of paramagnetic molecules such as nitric oxide (Litfi n et al ., 1980 ;Adams et al ., 1984 ;Ganser et al ., 2003 ;Fritsch et al ., 2008 ;Sabana et al , 2009 ;Lewicki et al ., 2009 ;Kluczynski et al ., 2011 ), nitrogen dioxide (Dillenschneider and Curl, 1983 ;Smith et al , 1995 ), oxygen (Brecha et al ., 1997 ;So et al ., 2011 ) and hydroxyl radicals (Pfeiffer et al ., 1981 ;Zhao et al , 2011 ). This technique takes advantage of the dispersion effects of paramagnetic molecules immersed in a longitudinal magnetic fi eld to reveal their unique property to rotate light polarization.…”

Section: Faraday Rotation Spectroscopy (Frs)mentioning

confidence: 99%

Tunable mid-infrared laser absorption spectroscopy

Tittel

Lewicki

2013

Semiconductor Lasers

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“…When the 2 approaches were compared on the NO fundamental (9), FRS sensitivity was found to be an order of magnitude better than the LMRS technique. FRS has been used as an extremely sensitive technique for the detection of paramagnetic molecules such as NO (1,7,(10)(11)(12), nitrogen dioxide (8,13), oxygen (14), or hydroxyl radicals (15). FRS is well suited for atmospheric measurements of free radicals (16) or for exhaled breath analysis because interference from diamagnetic species (such as water and carbon dioxide) is eliminated.…”

Section: Frsmentioning

confidence: 99%

Ultrasensitive detection of nitric oxide at 5.33 μm by using external cavity quantum cascade laser-based Faraday rotation spectroscopy

Lewicki

Doty

Curl

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

138

109

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A transportable prototype Faraday rotation spectroscopic system based on a tunable external cavity quantum cascade laser has been developed for ultrasensitive detection of nitric oxide (NO). A broadly tunable laser source allows targeting the optimum Q 3/2(3/2) molecular transition at 1875.81 cm ؊1 of the NO fundamental band. For an active optical path of 44 cm and 1-s lock-in time constant minimum NO detection limits (1) of 4.3 parts per billion by volume (ppbv) and 0.38 ppbv are obtained by using a thermoelectrically cooled mercury-cadmium-telluride photodetector and liquid nitrogen-cooled indium-antimonide photodetector, respectively. Laboratory performance evaluation and results of continuous, unattended monitoring of atmospheric NO concentration levels are reported.external cavity laser ͉ nitric oxide detection ͉ midinfrared ͉ magnetic circular birefringence ͉ paramagnetic species I n this article, we describe the development and performance of a prototype transportable, cryogen-free spectroscopic sensing system for ultrasensitive detection of atmospheric nitric oxide (NO) based on Faraday rotation spectroscopy (FRS). The FRS technique as a method for improving sensitivity by reducing source noise was first reported in the 1980s with a color-center laser source (1). The recent availability of thermoelectrically cooled widely tunable continuous wave (CW) external cavity quantum cascade lasers (EC-QCLs) (2) makes feasible a transportable FRS NO sensor targeting the optimum Q 3/2 (3/2) NO absorption line of the fundamental vibration at 5.33 m that has great potential for development into a compact field-deployable system. Ultrasensitive trace gas detection is of increasing interest in various applications including environmental monitoring, industrial emission measurements, chemical analysis, medical diagnostics, and security. The combination of midinfrared, continuous wave, high-performance QCL sources with sensitive spectroscopic measurement techniques is leading to improved specificity, and lower minimum detection limits (MDLs) for many molecular species as compared with nonoptical chemical sensors. This work was made possible by recent advances in QCL fabrication technology that have resulted in Fabry-Perot QC laser chips with wide gain bandwidth and high-output power levels at room temperature (3). These developments permit the construction of widely tunable EC-QCLs like the one used here.Our development of an EC-QCL-based FRS spectrometer was motivated by the current need for monitoring and quantifying the significant increase of atmospheric NO concentration levels due to combustion emissions that are impacting air quality in urban environments worldwide. NO molecules play a major role in atmospheric chemistry and significantly contribute to the formation of photochemical smog and acid rain and to the depletion of the stratospheric ozone layer (4, 5). Furthermore, NO at low concentrations in human and mammalian cells is of great importance in the regulation of biological and physiological processes (6). ...

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Sensitive magnetic rotation spectroscopy of the OH free radical fundamental band with a colour centre laser

Cited by 31 publications

References 10 publications

Cryogen-free heterodyne-enhanced mid-infrared Faraday rotation spectrometer

Cryogen-free heterodyne-enhanced mid-infrared Faraday rotation spectrometer

Tunable mid-infrared laser absorption spectroscopy

Ultrasensitive detection of nitric oxide at 5.33 μm by using external cavity quantum cascade laser-based Faraday rotation spectroscopy

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