Astigmatic mirror multipass absorption cells for long-path-length spectroscopy

McManus, J. Barry; Kebabian, Paul L.; Zahniser, M. S.

doi:10.1364/ao.34.003336

Cited by 367 publications

(189 citation statements)

References 14 publications

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“…The TILDAS technique for measuring NO 2 has been described in detail elsewhere (Li et al, 2004) and only a brief description is presented here. TILDAS is a tunable infrared laser differential absorption measurement that employs a low volume, long path length astigmatic Herriott multipass absorption cell (McManus et al, 1995) with liquid nitrogen cooled laser infrared diodes and detectors. The laser line width is small compared to the width of the absorption feature and the laser frequency position is rapidly swept over an entire absorption feature of the molecule to be detected, NO 2 in this case.…”

Section: Measurementsmentioning

confidence: 99%

Evaluation of nitrogen dioxide chemiluminescence monitors in a polluted urban environment

et al. 2007

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Abstract. Data from a recent field campaign in Mexico City are used to evaluate the performance of the EPA Federal Reference Method for monitoring the ambient concentrations of NO 2 . Measurements of NO 2 from standard chemiluminescence monitors equipped with molybdenum oxide converters are compared with those from Tunable Infrared Laser Differential Absorption Spectroscopy (TILDAS) and Differential Optical Absorption Spectroscopy (DOAS) instruments. A significant interference in the chemiluminescence measurement is shown to account for up to 50% of ambient NO 2 concentration during afternoon hours. As expected, this interference correlates well with non-NO x reactive nitrogen species (NO z ) as well as with ambient O 3 concentrations, indicating a photochemical source for the interfering species. A combination of ambient gas phase nitric acid and alkyl and multifunctional alkyl nitrates is deduced to be the primary cause of the interference. Observations at four locations at varying proximities to emission sources indicate that the percentage contribution of HNO 3 to the interference decreases with time as the air parcel ages. Alkyl and multifunctional alkyl nitrate concentrations are calculated to reach concenCorrespondence to: E. J. Dunlea (edward.dunlea@colorado.edu) trations as high as several ppb inside the city, on par with the highest values previously observed in other urban locations. Averaged over the MCMA-2003 field campaign, the chemiluminescence monitor interference resulted in an average measured NO 2 concentration up to 22% greater than that from co-located spectroscopic measurements. Thus, this interference has the potential to initiate regulatory action in areas that are close to non-attainment and may mislead atmospheric photochemical models used to assess control strategies for photochemical oxidants.

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Section: Measurementsmentioning

confidence: 99%

Evaluation of nitrogen dioxide chemiluminescence monitors in a polluted urban environment

et al. 2007

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“…The laser beam is extracted after a given 31 number of roundtrips, as limited by the available mirror area. An astigmatic variant of the Herriot cell has yielded 182 passes for a total path length of 100 m, based on a mirror separation of 0.55 m (McManus et al 1995).…”

Section: Introductionmentioning

confidence: 99%

Cavity Ring-Down and Cavity-Enhanced Detection Techniques for the Measurement of Aerosol Extinction

Moosmüller

Varma

Arnott

2005

Aerosol Science and Technology

100

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An instrument employing cavity ring-down (CRD) and cavityenhanced detection (CED) for the local measurement of aerosol extinction is described and demonstrated. CRD measures the lifetime of photons in a high-quality optical cavity and thereby determines the sum of sample extinction between the cavity mirrors and that due to mirror losses. CRD systems can be calibrated with a single gas for the determination of extinction. A green laser emitting subnanosecond pulses is used as a light source, facilitating measurements free from optical interference in the cavity. The addition of a low-frequency chopper allows for the determination of extinction coefficients with simple linear fitting procedures and also facilitates CED measurements by providing laser power modulation for phase-sensitive detection. CED measures the average power transmitted by the optical cavity. After calibration with two gases, CED allows for the independent measurement of extinction with very high dynamic range and for an independent comparison with CRD measurements, thereby increasing confidence in the measurements.

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“…The calculated offset uncertainty of SEALDH-II is reciprocally correlated with the optical path length. Therefore, an increase of the current 1.5 m optical path length to, e.g., 30 m or more with different cell designs such as McManus et al (1995) or Tuzson et al (2013) would allow us to reduce the offset uncertainty to 0.15 ppmv; the above-discussed laboratory offset deviation performance could reach levels of down to ±0.015 ppmv.…”

Section: Discussionmentioning

confidence: 99%

Absolute, pressure-dependent validation of a calibration-free, airborne laser hygrometer transfer standard (SEALDH-II) from 5 to 1200 ppmv using a metrological humidity generator

Buchholz

Ebert

2018

Atmos. Meas. Tech.

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Abstract. Highly accurate water vapor measurements are indispensable for understanding a variety of scientific questions as well as industrial processes. While in metrology water vapor concentrations can be defined, generated, and measured with relative uncertainties in the single percentage range, field-deployable airborne instruments deviate even under quasistatic laboratory conditions up to 10–20 %. The novel SEALDH-II hygrometer, a calibration-free, tuneable diode laser spectrometer, bridges this gap by implementing a new holistic concept to achieve higher accuracy levels in the field. We present in this paper the absolute validation of SEALDH-II at a traceable humidity generator during 23 days of permanent operation at 15 different H2O mole fraction levels between 5 and 1200 ppmv. At each mole fraction level, we studied the pressure dependence at six different gas pressures between 65 and 950 hPa. Further, we describe the setup for this metrological validation, the challenges to overcome when assessing water vapor measurements on a high accuracy level, and the comparison results. With this validation, SEALDH-II is the first airborne, metrologically validated humidity transfer standard which links several scientific airborne and laboratory measurement campaigns to the international metrological water vapor scale.

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Astigmatic mirror multipass absorption cells for long-path-length spectroscopy

Cited by 367 publications

References 14 publications

Evaluation of nitrogen dioxide chemiluminescence monitors in a polluted urban environment

Evaluation of nitrogen dioxide chemiluminescence monitors in a polluted urban environment

Cavity Ring-Down and Cavity-Enhanced Detection Techniques for the Measurement of Aerosol Extinction

Absolute, pressure-dependent validation of a calibration-free, airborne laser hygrometer transfer standard (SEALDH-II) from 5 to 1200 ppmv using a metrological humidity generator

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