Near-surface reduction of cavity ring-down spectroscopy detection sensitivity

Zhao, Maosheng; Wahl, E.H.; Owano, T. G.; Largent, Craig C.; Zare, Richard N.; Kruger, C.H.

doi:10.1016/s0009-2614(00)00090-7

Cited by 9 publications

(3 citation statements)

References 7 publications

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“…An increase near the sample surface can be observed, which is explained by the solid surface geometrical obstruc tion of the cavity ringdown beam and by the diffraction effects [50]. The near sample surface effects are diminished if instead of maximum of the absorption lines, an integrated intensity (gray area in figure 6 and an integral part of the equa tion (1)) is used.…”

Section: Resultsmentioning

confidence: 98%

Metastable helium atom density in a single electrode atmospheric plasma jet during sample treatment

Zaplotnik

Bišćan

Popović

et al. 2016

Plasma Sources Sci. Technol.

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The metastable He atoms play an important role in atmospheric pressure plasma jet (APPJ) chemistry processes and in the plasma generation. This work presents cavity ringdown spectroscopy (CRDS) investigation of metastable helium atom (2 S 3 1 ) densities in a single electrode APPJ during sample treatment. A spatially resolved density distribution of a free jet (without sample) was measured at a He flow rate of 2 slm. The maximum measured density of a free jet was around × 7 10 11 cm −3 . With the insertion of a sample the densities increased up to 10 times. Helium metastable atoms, in a single electrode helium APPJ (2 slm, ≈2.5 kV, pulsed DC, 10 kHz repetition rate), decayed exponentially with a mean lifetime of ± 0.27 0.03 μs. Eight different samples of the same sizes but different conductivities were used to investigate the influence of a sample material on the He metastable densities. The correlation between sample conductivities and metastable He densities above the sample surface was found. Metastable He density can also be further increased with decreasing sample distance, increasing conductive sample surface area and by increasing He flow.

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Section: Resultsmentioning

confidence: 98%

Metastable helium atom density in a single electrode atmospheric plasma jet during sample treatment

Zaplotnik

Bišćan

Popović

et al. 2016

Plasma Sources Sci. Technol.

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“…By eliminating rays that fall outside the aperture of any optic, this method properly accounts for rays that constitute bad injections (e.g., rays that strike the main cavity walls) or that do not strike the detector. Although this calculation is incomplete in that it does not include diffraction effects (which are important when beams fall near to the main cavity walls 39 ), it provides a quantitatively and qualitatively accurate prediction of the re-injection efficiency.…”

Section: Simulation Of Re-injection Performancementioning

confidence: 99%

Optical re-injection in cavity-enhanced absorption spectroscopy

Leen¹,

O’Keefe²

2014

Review of Scientific Instruments

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Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10 −10 cm −1 / √ Hz; an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features. © 2014 AIP Publishing LLC. [http://dx

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“…In applying CRDS to nanoliter-volume systems, it is necessary to focus the beam through an aperture that is generally <100 μm. To avoid diffraction losses and, thus, a reduction in the ring-down time constant, the Gaussian beam waist should be at least 4.6 times smaller than the aperture, a condition discussed by Siegman and verified experimentally by Zhao et al Such a tightly focused beam in a stable resonator is difficult to achieve because confocal or near-confocal geometry is required. The application of CRDS to nanoliter-volume systems is an area of interest because detection limits for these low-volume techniques are comparatively quite high, owing to the short path length of capillaries.…”

Section: Discussionmentioning

confidence: 99%

Cavity Ring-Down Spectroscopy as a Detector for Liquid Chromatography

Snyder

Zare

2003

Anal. Chem.

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We have demonstrated the use of cavity ring-down spectroscopy (CRDS) as a detector for high performance liquid chromatography (HPLC). For this use, we have designed and implemented a Brewster's angle flow cell such that cavity ring-down spectroscopy can be performed on microliter volumes of liquids. The system exhibits a linear dynamic range of 3 orders of magnitude (30 nM to 30 microM quinalizarin at 470 nm) for static measurements and 2 orders of magnitude (0.5 microM to 50 microM) for HPLC measurements. For the static measurements, the baseline noise is 2.8 x 10(-6) AU rms and 1.0 x 10(-5) AU peak-to-peak, and for the HPLC separations, it is 3.2 x 10(-6) AU rms and 1.3 x 10(-5) AU peak-to-peak. The baseline noise is determined after the data are smoothed by an 11-point boxcar average. The peak areas detected from HPLC separations are reproducible to within 2-3%. The HPLC mass detection limit for a molecule with epsilon = 9 x 10(3) M(-1) cm(-1) in a 300-microm path length cell (illuminated volume, 0.5 microL) is reported as 2.5 x 10(-8) g/mL. These results were obtained using a simple pulsed CRDS system and are comparable to, if not better than, a high-quality commercial UV-vis absorption detector for the same path length.

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Near-surface reduction of cavity ring-down spectroscopy detection sensitivity

Cited by 9 publications

References 7 publications

Metastable helium atom density in a single electrode atmospheric plasma jet during sample treatment

Metastable helium atom density in a single electrode atmospheric plasma jet during sample treatment

Optical re-injection in cavity-enhanced absorption spectroscopy

Cavity Ring-Down Spectroscopy as a Detector for Liquid Chromatography

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