Laser bandwidth effects in quantitative cavity ring-down spectroscopy

Hodges, Joseph T.; Looney, J. P.; Zee, Roger D. van

doi:10.1364/ao.35.004112

Cited by 123 publications

(81 citation statements)

References 10 publications

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“…The effect of laser bandwidth is unimportant for aerosols, since particle extinction is a broadband feature (Hodges et al 1996). The effects of laser phase noise are mainly important for continuous wave (cw)-CRDS (Morville et al 2002), due to the tight overlap of bandwidth and cavity mode width.…”

Section: The Crdsmentioning

confidence: 99%

Error Analysis and Uncertainty in the Determination of Aerosol Optical Properties Using Cavity Ring-Down Spectroscopy, Integrating Nephelometry, and the Extinction-Minus-Scattering Method

Singh

Fiddler

Smith

et al. 2014

Aerosol Science and Technology

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Despite the substantial improvements in the measurements of aerosol physical and chemical properties and in the direct and indirect radiative effects of aerosols, there is still a need for studying the properties of aerosols under controlled laboratory conditions to develop a mechanistic and quantitative understanding of aerosol formation, chemistry, and dynamics. In this work, we present the factors that affect measurement accuracy and the resulting uncertainties of the extinction-minus-scattering method using a combination of cavity ring-down spectroscopy (CRDS) and integrating nephelometry at a wider range of optical wavelengths than previously attempted. Purely scattering polystyrene latex (PSL) spheres with diameters from 107-303 nm and absorbing polystyrene spheres (APSL) with 390 nm diameter were used to determine the consistency and agreement, within experimental uncertainties, of CRDS and nephelometer values with theoretical calculations derived from Mie theory for non-absorbing spheres. Overall uncertainties for extinction cross-section were largely 10%-11% and dominated by condensation particle counter (CPC) measurement error. Two methods for determining σ ext error are described, and they were found to produce equivalent results. Systematic uncertainties due to particle losses, RD cell geometry (R L ), CPC counting efficiency, ring-down regression fitting, blank drift, optical tweezing, and recapturing of forward scattered light are also investigated. The random error observed in this work for absorbing spheres is comparable to previous reported measurements. For both absorbing and non-absorbing spheres, a statistical framework is developed for including the contributions to random error due to CPC measurement uncertainty, R L , statistical fluctuations in

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Section: The Crdsmentioning

confidence: 99%

Error Analysis and Uncertainty in the Determination of Aerosol Optical Properties Using Cavity Ring-Down Spectroscopy, Integrating Nephelometry, and the Extinction-Minus-Scattering Method

Singh

Fiddler

Smith

et al. 2014

Aerosol Science and Technology

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“…This phenomenon has been discussed extensively in the literature. [11][12][13] Research to extend the present analysis to cover this case is in progress in our laboratory. An important ingredient is the analysis of all decay transients obtained at various frequency settings over the line profile in one procedure; hence an ensemble fit is performed over all data to yield absolute absorption cross sections of narrow molecular absorption features.…”

Section: Discussionmentioning

confidence: 98%

“…In certain experimental conditions the frequency spectrum of a CRD cavity is white, a necessary condition for retrieving absolute absorption cross sections with pulsed CRD spectroscopy. 13 For a well-aligned setup a reliable estimate of the absolute number of photons in the cavity can be given at any time during the decay. With the numbers of photons in the cavity known it is possible to investigate quantitatively intensity-dependent absorptions with the CRD technique.…”

Section: Discussionmentioning

confidence: 99%

“…The problems associated with the nonzero bandwidth of the laser source, in particular in the regime where it is nonnegligible with respect to the width of the molecular absorption features, have been dis-cussed by Jongma et al, 11 Zalicki and Zare, 12 and Hodges et al 13 These problems are similar to the slit-function problem encountered in classical linear absorption spectroscopy. However, correction for these effects in CRDS is nontrivial, inasmuch as each frequency component within the laser bandwidth profile gives rise to a different decay time, thus producing multiexponential decay.…”

Section: Introductionmentioning

confidence: 95%

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Quantitative analysis of decay transients applied to a multimode pulsed cavity ringdown experiment

et al. 2001

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The intensity and noise properties of decay transients obtained in a generic pulsed cavity ringdown experiment are analyzed experimentally and theoretically. A weighted nonlinear least-squares analysis of digitized decay transients is shown that avoids baseline offset effects that induce systematic deviations in the estimation of decay rates. As follows from simulations not only is it a method that provides correct estimates for the values of the fit parameters, but moreover it also yields a correct estimate of the precision of the fit parameters. It is shown experimentally that a properly aligned stable optical resonator can effectively yield monoexponential decays under multimode excitation. An on-line method has been developed, based on a statistical analysis of the noise properties of the decay transients, to align a stable resonator toward this monoexponential decay.

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“…Furthermore, Zalicki and Zare [24] have shown that for small absorptions the measured integrated absorption deviates only slightly from the true integrated absorption, again as in a traditional absorption measurement. Several authors have investigated the bandwidth effect in CRDS [18,[24][25][26][27].…”

Section: A More Refined Picturementioning

confidence: 99%