UV spectrum and kinetics of hydroxymethyl radicals

Pagsberg, P.; Munk, Jette; Sillesen, Alfred; Anastasi, Christopher

doi:10.1016/0009-2614(88)87462-1

Cited by 78 publications

(73 citation statements)

References 15 publications

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“…In arriving at a recommendation for k 1 we reduced the weighting of the original absolute study by Michael et al [14], which lies considerably above the mean of the other values, and that of Wallington et al [17] which is not thought to be as reliable as the present study. Several of the studies [16,20] were not explicitly designed to measure k 1 and these studies have been given weights of 0.5 in the analysis, as has the study by Lightfoot et al [18] [17,21 -24]. The reasons for these discrepancies are not apparent, though.…”

Section: Discussionmentioning

confidence: 94%

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Rate coefficients for the reactions of chlorine atoms with methanol and acetaldehyde

et al. 1999

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Rate coefficients have been measured for the reactions of Cl atoms with methanol (k 1 ) and acetaldehyde (k 2 ) using both absolute (laser photolysis with resonance fluorescence) and relative rate methods at 295 Ϯ 2 K. The measured rate coefficients were (units of 10Based on a critical evaluation of the literature data, the following rate coefficients are recommended: k 1 ϭ (5.4 Ϯ 0.9) ϫ 10 Ϫ11 and k 2 ϭ (7.8 Ϯ 1.3) ϫ 10 Ϫ11 cm 3 molecule Ϫ1 s Ϫ1 (95% confidence limits). The results significantly improve the confidence in the database for reactions of Cl atoms with these oxygenated organics. Rate coefficients were also measured for the reactions of Cl 2 with CH 2 OH, k 5 ϭ (2.9 Ϯ 0.6) ϫ 10 Ϫ11 and CH 3 CO, k 6 ϭ (4.3 Ϯ 1.5) ϫ 10 Ϫ11 cm 3 molecule Ϫ1 s Ϫ1 , by observing the regeneration of Cl atoms in the absence of O 2 . Based on these results and those from a previous relative rate study, the rate coefficient for CH 3 CO ϩ O 2 at the high pressure limit is estimated to be (5.7 Ϯ 1.9) ϫ 10 Ϫ12 cm 3 molecule Ϫ1 s

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Section: Discussionmentioning

confidence: 94%

“…Figure 3 shows the second-order plots after correction for regeneration of Cl atoms. The influence of secondary reactions of Cl atoms with the free radical products, which are known to be very fast [12,13,16,34], also has to be considered. For the radical densities used, less than 1 ϫ 10 12 molecule cm…”

Section: Direct Measurement Of K 1 and Kmentioning

confidence: 99%

Rate coefficients for the reactions of chlorine atoms with methanol and acetaldehyde

et al. 1999

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“…• C For the C O bond cleavage reaction, our results are based on the recombination rate constant of Pagsberg [9] and again the assumption of zero activation energy in concentration units. The consequences as seen in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…A summary of past work can be found in Table I [ 1,4,[8][9][10][11][12]. The recommendations of Marinov [1] for the three processes can be found in the second column.…”

Section: Past Workmentioning

confidence: 99%

Energy transfer effects during the multichannel decomposition of ethanol

Tsang

2004

Int J of Chemical Kinetics

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Rate constants and expressions for the initial processes in the decomposition of ethanol have been derived on the basis of existing experimental and estimated results. Energy transfer effects on the multichannel decomposition processes have been determined through the solution of the master equation and on the basis of exponential-down and step-ladder collisional transition models. The predominant (lower threshold) channel is unaffected by the presence of the upper channels and results for the two transition models can be brought into correspondence by using a somewhat higher value for the step-size down parameter in the stepladder model. For the upper channels and with an exponential-down model, the logarithms of the ratio of the rate constants between perturbed and unperturbed systems can be captured by a sigmoidal shaped curve. In the case of the step-ladder model, the logarithms of this ratio decreases monotonically. Initially, differences between the two models are small (after adjusting the step-size down parameter). The results are compared with the recent simulations of Marinov. The order of magnitude differences in rate constants have been traced to the inclusion in the present study of experimental results pertaining to decomposition and the reverse combination processes in addition to the proper treatment of energy transfer effects during multichannel decompositions. Some observations regarding the parameterization of this type of pressure dependent data for use in simulations are presented. C

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“…Lines of HCO (formyl radical, Blake et al 1984), which we also observed during our spectral search, needed an additional magnetic field generated by the solenoid coil (~200 G) to completely disappear. The observed weakness of the lines of the hydroxymethyl radical can presumably be imputed to its short lifetime, which is partly due to the fast reaction of CH 2 OH with Cl to yield H 2 CO and HCl, about one order of magnitude faster than the reaction of CH 3 OH with Cl (Aristov et al 2000;Pagsberg et al 1988), and to the distribution of the radical population between the tunnelling, fine and hyperfine sublevels.…”

Section: Production Of Ch 2 Ohmentioning

confidence: 99%

Laboratory detection of the rotational-tunnelling spectrum of the hydroxymethyl radical, CH₂OH

Bermúdez

Bailleux

Cernicharo

2017

A&A

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Context. Of the two structural isomers of CH 3 O, methoxy is the only radical whose astronomical detection has been reported through the observation of several rotational lines at 2 and 3 mm wavelengths. Although the hydroxymethyl radical, CH 2 OH, is known to be thermodynamically the most stable (by~3300 cm −1 ), it has so far eluded rotational spectroscopy presumably because of its high chemical reactivity. Aims. Recent high-resolution (~10 MHz) sub-Doppler rovibrationally resolved infrared spectra of CH 2 OH (symmetric CH stretching a-type band) provided accurate ground vibrational state rotational constants, thus reviving the quest for its millimeter-wave spectrum in laboratory and subsequently in space. Methods. The search and assignment of the rotational spectrum of this fundamental species were guided by our quantum chemical calculations and by using rotational constants derived from high-resolution IR data. The hydroxymethyl radical was produced by hydrogen abstraction from methanol by atomic chlorine. Results. Ninety-six b-type rotational transitions between the v = 0 and v = 1 tunnelling sublevels involving 25 fine-structure components of Q branches (with K a = 1 ← 0) and 4 fine-structure components of R branches (assigned to K a = 0 ← 1) were measured below 402 GHz. Hyperfine structure alternations due to the two identical methylenic hydrogens were observed and analysed based on the symmetry and parity of the rotational levels. A global fit including infrared and millimeter-wave lines has been conducted using Pickett's reduced axis system Hamiltonian. The recorded transitions (odd ∆K a ) did not allow us to evaluate the Coriolis tunnelling interaction term. The comparison of the experimentally determined constants for both tunnelling levels with their computed values secures the long-awaited first detection of the rotational-tunnelling spectrum of this radical. In particular, a tunnelling rate of 139.73 ± 0.10 MHz (4.6609(32) × 10 −3 cm −1 ) was obtained along with the rotational constants, electron spin-rotation interaction parameters and several hyperfine coupling terms. Conclusions. The laboratory characterization of CH 2 OH by millimeter-wave spectroscopy now offers the possibility for its astronomical detection for the first time.

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UV spectrum and kinetics of hydroxymethyl radicals

Cited by 78 publications

References 15 publications

Rate coefficients for the reactions of chlorine atoms with methanol and acetaldehyde

Rate coefficients for the reactions of chlorine atoms with methanol and acetaldehyde

Energy transfer effects during the multichannel decomposition of ethanol

Laboratory detection of the rotational-tunnelling spectrum of the hydroxymethyl radical, CH₂OH

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UV spectrum and kinetics of hydroxymethyl radicals

Cited by 78 publications

References 15 publications

Rate coefficients for the reactions of chlorine atoms with methanol and acetaldehyde

Rate coefficients for the reactions of chlorine atoms with methanol and acetaldehyde

Energy transfer effects during the multichannel decomposition of ethanol

Laboratory detection of the rotational-tunnelling spectrum of the hydroxymethyl radical, CH2OH

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Laboratory detection of the rotational-tunnelling spectrum of the hydroxymethyl radical, CH₂OH