An Introduction to Cavity Ring-Down Spectroscopy

Lehmann, K. K.; Berden, Giel; Engeln, Rah Richard

doi:10.1002/9781444130829.ch1

Cited by 10 publications

(11 citation statements)

References 51 publications

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“…Our recent study of Drosophila cryptochrome employed a continuous-wave cavity enhanced absorption method which, while offering high sensitivity with broadband spectral coverage, does not provide time-resolved data . The experiments reported below employ a pump–probe technique with detection by cavity ring-down spectroscopy (CRDS), which permits a detailed analysis of the time-, wavelength-, and magnetic field-dependence of the transient radicals. In CRDS, a laser light pulse is injected into a high-finesse optical cavity .…”

Section: Introductionmentioning

confidence: 99%

Magnetically Sensitive Radical Photochemistry of Non-natural Flavoproteins

et al. 2018

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It is a remarkable fact that ∼50 μT magnetic fields can alter the rates and yields of certain free-radical reactions and that such effects might be the basis of the light-dependent ability of migratory birds to sense the direction of the Earth's magnetic field. The most likely sensory molecule at the heart of this chemical compass is cryptochrome, a flavin-containing protein that undergoes intramolecular, blue-light-induced electron transfer to produce magnetically sensitive radical pairs. To learn more about the factors that control the magnetic sensitivity of cryptochromes, we have used a set of de novo designed protein maquettes that self-assemble as four-α-helical proteins incorporating a single tryptophan residue as an electron donor placed approximately 0.6, 1.1, or 1.7 nm away from a covalently attached riboflavin as chromophore and electron acceptor. Using a specifically developed form of cavity ring-down spectroscopy, we have characterized the photochemistry of these designed flavoprotein maquettes to determine the identities and kinetics of the transient radicals responsible for the magnetic field effects. Given the gross structural and dynamic differences from the natural proteins, it is remarkable that the maquettes show magnetic field effects that are so similar to those observed for cryptochromes.

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Section: Introductionmentioning

confidence: 99%

Magnetically Sensitive Radical Photochemistry of Non-natural Flavoproteins

et al. 2018

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“…CRDS increases the effective path length over which the light can interact with the sample by enclosing the sample between two (or more) highly reflective mirrors. 23 , 24 This work utilizes continuous-wave (cw) CRDS in which cw laser radiation is focused into an optical cavity formed from two dielectric mirrors, aligned such that cavity modes are readily and regularly excited. 25 − 28 The light intensity exiting the cavity is monitored, and when a certain threshold is reached, the laser radiation is switched off, causing the light intensity within the cavity to decay exponentially.…”

Section: Materials and Methodsmentioning

confidence: 99%

Determining Water Transport Kinetics in Limestone by Dual-Wavelength Cavity Ring-Down Spectroscopy

et al. 2022

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Water plays a major role in the deterioration of porous building materials such as those widely found in built heritage, influencing many physical, chemical, and biological decay processes. This article details a proof-of-principle study using near-infrared cavity ring-down spectroscopy (CRDS) to monitor the release of water and its artificially enriched isotopologues from small (ca. 25 × 25 × 5 mm) samples of limestone subject to drying by a fixed flow of nitrogen with varying levels of humidity and at room temperature and atmospheric pressure. Under low-humidity conditions, the drying kinetics are consistent with the well-established two-phase drying process exhibited by porous materials, namely, an initial constant drying rate period (phase I) followed by a falling drying rate period (phase II). The water diffusivity during phase II, D II , was measured (for Clipsham limestone) to be 3.0 × 10 –9 ± 1 × 10 –10 m 2 s –1 . The CRDS measurements allow spectroscopic determination of the total mass of water released by the sample, and the calculated values are in excellent agreement with gravimetric analysis. Importantly, the selectivity and sensitivity afforded by CRDS allows isotope analysis to be carried out, such that the flux of isotopically labeled water out of the sample can be determined under conditions of humidified flow where there may be a simultaneous ingress of water from the environment. Dual-wavelength CRDS distinguishes isotopic species, and it is demonstrated that the drying kinetics and physical properties of the samples are self-consistent when monitoring both HDO and H 2 O (for HDO, D II was 3.2 × 10 –9 ± 4 × 10 –10 m 2 s –1 ). As the humidity levels in the flow increase, a departure from the distinct two-phase behavior is observed in the HDO drying curves. These new measurements of isotopically resolved mass fluxes will help refine models for drying mechanisms in porous media.

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“…In this work, each LSF required about 50 ms, constraining the ring-down event rate to 20 Hz. This can be substantially improved using a specialized algorithm (Lehmann et al, 2009). On average, about 15 minutes was required to record 5,000 ring-downs for 13 CH 4 and the baseline, each, and 500 ringdowns for 12 CH 4 .…”

Section: Spectrometer Designmentioning

confidence: 99%