An experimental and computational study of the unimolecular-decay reaction of diethyl-substituted Criegee intermediate (CH)COO.

We have performed direct kinetic measurements to determine the thermal unimolecular-decay rate coefficient of (CH)COO as a function of temperature (223-296 K) and pressure (4-100 torr) using time-resolved UV-absorption spectroscopy. The stabilised (CH)COO Criegee intermediate was produced by photolysing 3-bromo-3-iodopentane ((CH)CIBr) with 213 nm radiation in the presence of O. We performed quantum-chemistry calculations and master-equation simulations to complement the experimental work.

Direct Kinetic Measurements of a Cyclic Criegee Intermediate; Unimolecular Decomposition of (CH)COO.

We report the first direct kinetic measurements of a cyclic stabilized Criegee Intermediate. We have measured the unimolecular reaction rate coefficient of cyclohexanone oxide ((CH)COO) in the temperature 213-296 K and pressure 7-50 Torr ranges using absorption spectrometry. The (CH)COO was produced by the photolysis of (CH)CIBr at 213 nm in the presence of O.

An Experimental and Master Equation Investigation of Kinetics of the CHOO + RCN Reactions (R = H, CH, CH) and Their Atmospheric Relevance.

We have performed direct kinetic measurements of the CHOO + RCN reactions (R = H, CH, CH) in the temperature range 233-360 K and pressure range 10-250 Torr using time-resolved UV-absorption spectroscopy. We have utilized a new photolytic precursor, chloroiodomethane (CHICl), whose photolysis at 193 nm in the presence of O produces CHOO. Observed bimolecular rate coefficients for CHOO + HCN, CHOO + CHCN, and CHOO + CHCN reactions at 296 K are (2.

Solving the discrepancy between the direct and relative-rate determinations of unimolecular reaction kinetics of dimethyl-substituted Criegee intermediate (CH)COO using a new photolytic precursor.

We have performed direct kinetic measurements of the thermal unimolecular reaction of (CH)COO in the temperature range 243-340 K and pressure range 5-350 Torr using time-resolved UV-absorption spectroscopy. We have utilized a new photolytic precursor, 2-bromo-2-iodopropane ((CH)CIBr), which photolysis at 213 nm in the presence of O produces acetone oxide, (CH)COO. The results show that the thermal unimolecular reaction is even more important main loss process of (CH)COO in the atmosphere than direct kinetic studies have suggested hitherto.

Time-resolved, broadband UV-absorption spectrometry measurements of Criegee intermediate kinetics using a new photolytic precursor: unimolecular decomposition of CHOO and its reaction with formic acid.

We present a time-resolved broadband cavity-enhanced UV-absorption spectrometer apparatus that we have constructed and utilized for temperature- and pressure-dependent kinetic measurements of formaldehyde oxide (CHOO) reactions. We also introduce and utilize a new photolytic precursor, bromoiodomethane (CHIBr), which photolysis at 213 nm in presence of O produces CHOO. Importantly, this precursor appears to be free from secondary reactions that may regenerate CHOO in kinetic experiments.

Parts-per-trillion-level detection of nitrogen dioxide by cantilever-enhanced photo-acoustic spectroscopy.

We present a simple and highly sensitive cantilever-enhanced photo-acoustic sensor for detection of nitrogen dioxide. A noise equivalent detection limit of 50 parts-per-trillion in 1 s is demonstrated. The limit was reached with an average optical power of 4.

Frequency-comb-referenced mid-infrared source for high-precision spectroscopy.

We report on a tunable continuous-wave mid-infrared optical parametric oscillator (OPO), which is locked to a fully stabilized near-infrared optical frequency comb using a frequency doubling scheme. The OPO is used for 40 GHz mode-hop-free, frequency-comb-locked scans in the wavelength region between 2.7 and 3.

High sensitivity trace gas detection by cantilever-enhanced photoacoustic spectroscopy using a mid-infrared continuous-wave optical parametric oscillator.

Highly sensitive cantilever-enhanced photoacoustic detection of hydrogen cyanide and methane in the mid-infrared region is demonstrated. A mid-infrared continuous-wave frequency tunable optical parametric oscillator was used as a light source in the experimental setup. Noise equivalent detection limits of 190 ppt (1 s) and 65 ppt (30 s) were achieved for HCN and CH(4), respectively.

Grating-cavity continuous-wave optical parametric oscillators for high-resolution mid-infrared spectroscopy.

The use of grating as a spectral filter provides a simple way of improving wavelength tuning and stability of continuous-wave optical parametric oscillators (cw OPOs). In this paper, we discuss how to design and use such grating-cavity cw OPOs for high-resolution spectroscopy in the molecular fingerprint region at ∼3μm. The first design presented in the paper is based on a metal-coated diffraction grating, which produces fast and broad wavelength tuning and high wavelength stability.

Continuous-wave optical parametric oscillator tuned by a diffraction grating.

A new continuous-wave singly resonant optical parametric oscillator is described. It is capable of stable, widely tunable single-frequency output in the mid-infrared region. A magnesium oxide doped periodically poled LiNbO(3) crystal provides the parametric amplification.

Singly resonant cw OPO with simple wavelength tuning.

A singly resonant continuous-wave optical parametric oscillator (cw OPO) is described. The OPO contains no intracavity etalon, which makes its wavelength tuning simple and straightforward, including only temperature tuning of the nonlinear crystal and wavelength tuning of the pump laser. The OPO provides watt-level output in the mid-infrared region and operates reliably without mode hops for several hours.