Microcontroller based resonance tracking unit for time resolved continuous wave cavity-ringdown spectroscopy measurements

Votava, Ondřej; Mašát, Milan; Parker, Alexander E.; Jain, Chaithania; Fittschen, C.

doi:10.1063/1.3698061

Cited by 34 publications

(37 citation statements)

References 15 publications

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“…The HO 2 yield,

Φ_{{HO}_{2}}

, has been obtained from the simultaneous measurement of OH and HO 2 concentration time profiles, using a laser photolysis reactor coupled to two identical continuous wave cavity ring down spectroscopy (cw‐CRDS) absorption paths. The experimental setup has already been described in detail . Briefly, the reaction was initiated by the 248 nm photolysis of XeF 2 in the presence of hydrocarbons RH (methane, ethane, propane [all with a purity of 99.95%; Air Liquide, France] or n ‐butane [purity 99.5%; Air Liquide, France]) and H 2 O, leading to the generation of the peroxy radicals and OH radicals through the following reaction sequence:

{XeF}_{2} + h υ_{248 nm} \to 2 F + Xe

RH + F \to R + HF

{normalH}_{2} O + F \to OH + HF

R + {normalO}_{2} (+ M) \to {RO}_{2}

which is followed by reaction (R1).…”

Section: Methodsmentioning

confidence: 99%

Experimental and theoretical investigation of the reaction of RO₂ radicals with OH radicals: Dependence of the HO₂ yield on the size of the alkyl group

Assaf

Schoemaecker

Vereecken

et al. 2018

Int J of Chemical Kinetics

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The HO2 yield in the reaction of peroxy radicals with OH radicals has been determined experimentally at 50 Torr helium by measuring simultaneously OH and HO2 concentration time profiles, following the photolysis of XeF2 in the presence of different hydrocarbons and O2. The following yields have been obtained: ϕ CH 3O2 = (0.90 ± 0.1), ϕC2H5O2 = (0.75 ± 0.15), ϕC3H7O2 = (0.41 ± 0.08), and ϕC4H9O2 = (0.15 ± 0.03). The clear decrease in HO2 yield with increasing size of the alkyl moiety can be explained by an increased stabilization of the trioxide adduct, ROOOH. This has been confirmed by ab initio and Rice–Ramsperger–Kassel–Marcus master equation calculations. Extrapolation of the experimental results to atmospheric conditions shows that the stabilized adduct, ROOOH, is the nearly exclusive product of the reaction between OH radicals and peroxy radicals containing more than three C‐atoms. The fate and possible impact of these species is completely unexplored so far.

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“…The HO 2 yield,

Φ_{{HO}_{2}}

{XeF}_{2} + h υ_{248 nm} \to 2 F + Xe

RH + F \to R + HF

{normalH}_{2} O + F \to OH + HF

R + {normalO}_{2} (+ M) \to {RO}_{2}

which is followed by reaction (R1).…”

Section: Methodsmentioning

confidence: 99%

Experimental and theoretical investigation of the reaction of RO₂ radicals with OH radicals: Dependence of the HO₂ yield on the size of the alkyl group

Assaf

Schoemaecker

Vereecken

et al. 2018

Int J of Chemical Kinetics

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“…A detailed description of the experimental setup has already been published and will therefore not be given here. We recently improved the acquisition system, as described by Votava et al : A microcontroller‐based unit tracked the piezo crystal and increased the rate of cw‐CRDS events, thus enhancing the signal‐to‐noise ratio. All data were acquired using an acquisition card (National Instruments PC‐6259) installed in a personal computer, and all programs were written in Labview, version 8.2.1.…”

Section: Methodsmentioning

confidence: 99%

Direct Measurement of the Equilibrium Constants of the Reaction of Formaldehyde and Acetaldehyde with HO₂ Radicals

Morajkar

Schoemaecker

Okumura

et al. 2013

Int J of Chemical Kinetics

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Rate and equilibrium constants for the reaction of HO2 with formaldehyde trueright130.79993pt CH 2normalO+ HO 2↔ HO CH 2O22.em2.em2.em2.em2.em2.em1em(normalR1) and acetaldehyde trueright118.79993pt CH 3 CHO + HO 2↔ CH 3 CH ( OH )O22.em2.em2.em2.em1em2.em(normalR2) have been directly measured. The concentration of HO2 radicals was followed in a time‐resolved method by coupling cw‐CRDS (cavity ringdown spectroscopy) to laser photolysis. The reaction of HO2 with CH2O (R1) was measured at 50 Torr helium over the temperature range 292–306 K, whereas the reaction of CH3CHO with HO2 (R2) was measured in 50 Torr He but at only 294 K. The observed HO2 decay profiles were modeled to take into account secondary chemistry, especially that of the reaction products, hydroxyl‐peroxy radical adducts. The rate constants for forward and back reactions of (R1) at 297 K were found to be k1 = (3.3 ± 0.6) × 10−14 cm3 molecule−1 s−1 and k−1 = (55 ± 5) s−1, respectively, both roughly a factor of two slower than earlier measurements (possibly due to falloff effects), while the equilibrium constant was found to be K1 = (6.0 ± 1.8) × 10−16 molecule−1 cm3 at 297 K, in good agreement with earlier, more indirect determinations. The equilibrium constant of the reaction with CH3CHO was found to be K2 = (1.7 ± 0.5) × 10−17 molecule−1 cm3 at 294 K, with the forward rate constant k2 = (1.5 ± 0.75) × 10−14 cm3 molecule−1 s−1 and the rate constant for the back reaction k−2 = (900 ± 450) s−1.

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“…in a simple non-time resolved manner, for the measurement of the CH 2 O absorption spectrum. The principle of this technique has been published previously [30], and recent improvements concerning the synchronization [31] and acquisition [32] can be found in more recent work. The mirrors used in this work (Los Gatos) had a reflectivity of R = 0.999954, leading to ring-down times in the empty cavity of around 60 ls.…”

Section: Methodsmentioning

confidence: 96%

“…Detailed description of this set-up has already been published [30,31] and an improvement recently made to the acquisition system has been described by Votava et al [32]. The photolysis cell has three axes and is made of stainless steel, internally coated with Teflon.…”

Section: Methodsmentioning

confidence: 99%

Absolute absorption cross sections for two selected lines of formaldehyde around 6625cm−1

Morajkar

Schoemaecker

Fittschen

2012

Journal of Molecular Spectroscopy

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Microcontroller based resonance tracking unit for time resolved continuous wave cavity-ringdown spectroscopy measurements

Cited by 34 publications

References 15 publications

Experimental and theoretical investigation of the reaction of RO₂ radicals with OH radicals: Dependence of the HO₂ yield on the size of the alkyl group

Experimental and theoretical investigation of the reaction of RO₂ radicals with OH radicals: Dependence of the HO₂ yield on the size of the alkyl group

Direct Measurement of the Equilibrium Constants of the Reaction of Formaldehyde and Acetaldehyde with HO₂ Radicals

Absolute absorption cross sections for two selected lines of formaldehyde around 6625cm−1

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Microcontroller based resonance tracking unit for time resolved continuous wave cavity-ringdown spectroscopy measurements

Cited by 34 publications

References 15 publications

Experimental and theoretical investigation of the reaction of RO2 radicals with OH radicals: Dependence of the HO2 yield on the size of the alkyl group

Experimental and theoretical investigation of the reaction of RO2 radicals with OH radicals: Dependence of the HO2 yield on the size of the alkyl group

Direct Measurement of the Equilibrium Constants of the Reaction of Formaldehyde and Acetaldehyde with HO2 Radicals

Absolute absorption cross sections for two selected lines of formaldehyde around 6625cm−1

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Experimental and theoretical investigation of the reaction of RO₂ radicals with OH radicals: Dependence of the HO₂ yield on the size of the alkyl group

Experimental and theoretical investigation of the reaction of RO₂ radicals with OH radicals: Dependence of the HO₂ yield on the size of the alkyl group

Direct Measurement of the Equilibrium Constants of the Reaction of Formaldehyde and Acetaldehyde with HO₂ Radicals