Cavity Ringdown Laser Absorption Spectroscopy

Wang, Chuji; Miller, George P.; Winstead, Chris

doi:10.1002/9780470027318.a5602m.pub2

Cited by 7 publications

(4 citation statements)

References 205 publications

(212 reference statements)

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“…Since isoprene has been identified as a potential biomarker associated with cholesterol synthesis, particular interest has been placed on accurately detecting and measuring its presence, especially in breath gas [32,33,37-40]. At 266 nm, there is a distinction between the UV spectra of isoprene and pentane.…”

Section: Resultsmentioning

confidence: 99%

Measurements of the Weak UV Absorptions of Isoprene and Acetone at 261–275 nm Using Cavity Ringdown Spectroscopy for Evaluation of a Potential Portable Ringdown Breath Analyzer

Sahay

Scherrer

Wang

2013

Sensors

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The weak absorption spectra of isoprene and acetone have been measured in the wavelength range of 261–275 nm using cavity ringdown spectroscopy. The measured absorption cross-sections of isoprene in the wavelength region of 261–266 nm range from 3.65 × 10−21 cm2·molecule−1 at 261 nm to 1.42 × 10−21 cm2·molecule−1 at 266 nm; these numbers are in good agreement with the values reported in the literature. In the longer wavelength range of 270–275 nm, however, where attractive applications using a single wavelength compact diode laser operating at 274 nm is located, isoprene has been reported in the literature to have no absorption (too weak to be detected). Small absorption cross-sections of isoprene in this longer wavelength region are measured using cavity ringdown spectroscopy for the first time in this work, i.e., 6.20 × 10−23 cm2·molecule−1 at 275 nm. With the same experimental system, wavelength-dependent absorption cross-sections of acetone have also been measured. Theoretical detection limits of isoprene and comparisons of absorbance of isoprene, acetone, and healthy breath gas in this wavelength region are also discussed.

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Section: Resultsmentioning

confidence: 99%

Measurements of the Weak UV Absorptions of Isoprene and Acetone at 261–275 nm Using Cavity Ringdown Spectroscopy for Evaluation of a Potential Portable Ringdown Breath Analyzer

Sahay

Scherrer

Wang

2013

Sensors

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“…CRDS is a laser absorption spectral technique [178][179][180][181][182][183]. It achieves high sensitivity because of the multi-pass nature of the optical absorption path.…”

Section: Ot-crdsmentioning

confidence: 99%

Optical trapping and laser-spectroscopy measurements of single particles in air: a review

Wang¹,

Pan²,

Videen³

2021

Meas. Sci. Technol.

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From the early optical-tweezers approach, which uses a single tightly focused laser beam to levitate dielectric or absorbing micron-sized particles, to the recently developed optical traps such as the universal optical trap (UOT), which can trap particles of arbitrary chemical and physical properties in different media, optical trapping (OT) has evolved significantly over the last decades. Research in OT has been extended from single-particle control to single-particle measurements. One of the most rapid developments in OT is the combination of OT with advanced laser spectroscopic techniques to achieve on-trap single-particle studies. To date, a wide variety of single particles including carbons, dusts, metal oxides, pollens, spores, organic/inorganic droplets, etc have been stably trapped in air and characterized using Raman spectroscopy, cavity ringdown spectroscopy, light scattering, or laser-induced breakdown spectroscopy, etc. As single particles can be trapped stably in the UOT for long periods of time, temporal evolution of the chemical and physical properties of trapped particles can also be studied. Very recently, even chemical reactions of a single particle under controlled atmospheric environments have been investigated. This review updates the most recent developments in OT, with a particular emphasis on laser-spectroscopy measurements of single particles trapped in air.

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“…Although Abel inversion can be used to obtain a radial density profile from the line-of-sight measurement [50], unless otherwise stated, the density referred to in the following text is the line-of-sight density. The absolute density in the initial rotational energy level of the OH S 21 (1) transition can be derived from ringdown measurements by [51,52]…”

Section: Measurements Of Oh Radicals Using Crdsmentioning

confidence: 99%

Optical diagnostics of a low power—low gas flow rates atmospheric-pressure argon plasma created by a microwave plasma torch

Wang

Srivastava

Scherrer

et al. 2009

Plasma Sources Sci. Technol.

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We employ a suite of optical techniques, namely, visual imaging, optical emission spectroscopy and cavity ringdown spectroscopy (CRDS), to characterize a low power, low gas flow rates, atmospheric-pressure argon microwave induced plasma. The plasma is created by a microwave plasma torch, which is excited by a 2.45 GHz microwave with powers ranging from 60 to 120 W. A series of plasma images captured in a time-resolution range of as fine as 10 µs shows that the converging point is actually a time-averaged visual effect and the converging point does not exist when the plasma is visualized under high time resolution, e.g. <2 ms. Simulations of the emission spectra of OH, N 2 and N + 2 in the range 200-450 nm enable the plasma electronic excitation temperature (T exc ) to be determined at 8000-9000 K, while the vibrational temperature (T v ), the rotational temperature (T r ) and the gas temperature (T g ) at different locations along the axis of the plasma column are all determined to be in the range 1800-2200 K. Thermal equilibrium properties of the plasma are discussed. OH radical concentrations along the plasma column axis are measured by CRDS and the concentrations are in the range 1.6 × 10 13 -3.0 × 10 14 cm −3 with the highest density at the tail of the plasma column. The upper limit of electron density n e is estimated to be 5.0 × 10 14 cm −3 from the Lorentzian component of the broadened lineshape obtained by ringdown spectral scans of the rovibrational line S 21 of the OH A-X (0-0) band.

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Cavity Ringdown Laser Absorption Spectroscopy

Cited by 7 publications

References 205 publications

Measurements of the Weak UV Absorptions of Isoprene and Acetone at 261–275 nm Using Cavity Ringdown Spectroscopy for Evaluation of a Potential Portable Ringdown Breath Analyzer

Measurements of the Weak UV Absorptions of Isoprene and Acetone at 261–275 nm Using Cavity Ringdown Spectroscopy for Evaluation of a Potential Portable Ringdown Breath Analyzer

Optical trapping and laser-spectroscopy measurements of single particles in air: a review

Optical diagnostics of a low power—low gas flow rates atmospheric-pressure argon plasma created by a microwave plasma torch

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