Free jet-cooled laser-induced fluorescence spectrum of methoxy. 1. Vibronic analysis of the ~A and ~X states

Foster, Stephen; Misra, Prabhakar; Lin, Tay-Jyi; Damo, Cristino P.; Carter, Christopher C.; Miller, Terry A.

doi:10.1021/j100332a014

Cited by 117 publications

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“…Although this structure has been seen in many of the other studies on methoxy 12,14,15,20 there is some disagreement in the literature as to which of these components can be better Table II). …”

Section: A Symmetric Modesmentioning

confidence: 77%

“…Experimentally, the radical can be conveniently studied by a variety of optical techniques for which the strong oscillator strength of the transition from the ground state to the first excited state ( A 2 A 1 ↔ X 2 E) lends itself well to laser induced fluorescence [8][9][10][11][12][13][14][15][16][17][18] (LIF) and dispersed fluorescence (and emission) 10,12,13,16,[18][19][20][21] and more recently stimulated emission pumping (SEP) studies. 22 Such experiments have led to considerable knowledge about the vibrational frequencies in the ground and excited electronic states.…”

Section: Introductionmentioning

confidence: 99%

“…Various jet expansion studies [9][10][11][12]14,15,18,20 have been performed over the past 15 years and a number of the vibrational frequencies have been determined for the A excited state but there have also been some problems associated with these studies. For a considerable time, even the frequency of the origin of the electronic transition was under dispute with a variety of values reported in the literature (for more information see Foster et al 12 ).…”

Section: Introductionmentioning

confidence: 99%

“…The synthesis of the methyl nitrite, as described previously 12 , was made by dropwise addition of dilute sulfuric acid to a solution of sodium nitrite and methyl alcohol. The gaseous product was collected and used from a reservoir held at the temperature of a dry ice isopropyl alcohol bath.…”

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confidence: 99%

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Rovibronic analysis of the laser induced fluorescence excitation spectrum of the jet-cooled methoxy radical

Powers

Pushkarsky

Miller

1997

The Journal of Chemical Physics

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The laser induced fluoresence excitation spectrum for the A 2 A 1 ↔ X 2 E transition of the methoxy radical has been reinvestigated. An extensive set of vibrational levels has been assigned with the aid of increased vibrational and rotational cooling. Many of these vibrational assignments are confirmed by rotational analysis of bands involving both the symmetric and asymmetric fundamentals of the A state as well as vibrations containing two quanta of the e modes. Although parts of the vibrational structure have been assigned previously, several discrepancies are identified and corrected. Vibrational frequencies have been obtained for all the modes in the A 2 A 1 state of the molecule. The Fermi resonance that exists between ν 3 and ν 2 has been investigated and interaction constants describing it have been obtained.

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Section: A Symmetric Modesmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Rovibronic analysis of the laser induced fluorescence excitation spectrum of the jet-cooled methoxy radical

Powers

Pushkarsky

Miller

1997

The Journal of Chemical Physics

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“…c******************************************************************** (22) close (23 ) close (24) close ( 2 5 ) close (26) write (6,") 'Wrote raw2d.dat,z2d.dat,deltar2d.dat' sqrt (Ptheta(itheta) ) /sin(theta) end do c note that the 90 degree point is split evenly between +z and -z; these c two must be summed to form a full one degree angle we 1 gh t ed c uith the other angle bins …”

Section: B Outputmentioning

confidence: 99%

Photodissociation dynamics and spectroscopy of free radical combustion intermediates

Osborn

1996

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The photodissociation spectroscopy and dynamics of free radicals is studied by the technique of fast beam photofragment translational spectroscopy. Photodetachment of internally cold, mass-selected negative ions produces a clean source of radicals, which are subsequently dissociated and detected. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic states of the radical. In addition, the photodissociation dynamics, product branching ratios, and bond energies are probed at fned photon energies by measuring the translational energy, ET), and angular distribution of the recoiling fragments using a time-and positionsensitive detector. Ab initio calculations are combined with dynamical and statistical models to interpret the observed data.The photodissociation of three prototypical hydrocarbon combustion intermediates forms the core of this work. The methoxy radical (CH30), the vinoxy radical (CH2CHO) 2 and the ketenyl radical (HCCO), are representative examples of alkanoxy, alkenoxy, and alkynoxy radicals, respectively. The dominant channel in methoxy dissociation following ultraviolet excitation is CH30 + CH3 + 0. Vibrational structure is resolved in the P(&) distribution, and a new heat of formation is obtained for CH30. Two primary channels are active in vinoxy photodissociation: CH2CHO + CH3 + CO, and CH2CHO + CH2CO + H. The dissociation dynamics in vinoxy occur by internal conversion to the ground state followed by dissociation over a barrier to products. The ketenyl radical is observed for the first time in the ultraviolet, dissociating via two distinct channels: HCCO + CH X(213) + CO, and HCCO -+ CH u (~C -) + CO. The dynamics in this case occur by internal conversion and intersystem crossing, followed by dissociation on potential surfaces with negligible barriers to products. The branching ratio is a function of photon energy, and a heat of formation is determined for ketenyl.In addition, the photodissociation of a negative ion radical, N202-, is also explored.This ion photodissociates via two channels: N20F + 0-+ N20, and N20; + NO-+ NO.Product vibrational structure is observed in the N20 bending mode, and a heat of formation is obtained for N202-. However, even in the relatively well-defined limit of a crossed molecular beam experiment, in which the reactants approach and the products are detected along defined trajectories, the results are inherently averaged over a range of impact parameters describing the difference between head-on and glancing collisions of the reactants. One way to avoid averaging over the impact parameter in the bimolecular "full collision" described above is to simpllfv the system by studying the unimolecular "half collision" of Is there more than one product channel participating?What is the bond strength, of AHm for each channel?How fast ,does dissociation take place?How is the excess energy distributed among the products?Can we determine the dissociation mechanism from this information?For the s...

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Preparation of Single Rotation Vibration States of CH₃O (X̃²E) Above the H – CH₂O Dissociation Threshold by Stimulated Emission Pumping

Geers

Kappert

Temps

et al. 1990

Ber Bunsenges Phys Chem

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By the technique of Stimulated Emission Pumping (SEP), single high‐lying rotation vibration states of CH3O (X̃2E) with defined total energy Err and total angular momentum J were probed in the regime 3000 cm−1 ≤ Err ≤ 9300 cm−1, up to well above the H – CH2O asymptotic dissociation limit (≈ 6800 cm−1). Observed low resolution SEP spectra exhibit distinctive vibrational band structure. Spectra recorded at high resolution reflect intramolecular dynamical processes occuring on different time scales. The detailed spectroscopic characterization of the level structure of highly excited CH3O provides the basis for critical tests of models for unimolecular reactions.

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Free jet-cooled laser-induced fluorescence spectrum of methoxy. 1. Vibronic analysis of the ~A and ~X states

Cited by 117 publications

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Rovibronic analysis of the laser induced fluorescence excitation spectrum of the jet-cooled methoxy radical

Rovibronic analysis of the laser induced fluorescence excitation spectrum of the jet-cooled methoxy radical

Photodissociation dynamics and spectroscopy of free radical combustion intermediates

Preparation of Single Rotation Vibration States of CH₃O (X̃²E) Above the H – CH₂O Dissociation Threshold by Stimulated Emission Pumping

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Free jet-cooled laser-induced fluorescence spectrum of methoxy. 1. Vibronic analysis of the ~A and ~X states

Cited by 117 publications

References 0 publications

Rovibronic analysis of the laser induced fluorescence excitation spectrum of the jet-cooled methoxy radical

Rovibronic analysis of the laser induced fluorescence excitation spectrum of the jet-cooled methoxy radical

Photodissociation dynamics and spectroscopy of free radical combustion intermediates

Preparation of Single Rotation Vibration States of CH3O (X̃2E) Above the H – CH2O Dissociation Threshold by Stimulated Emission Pumping

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Preparation of Single Rotation Vibration States of CH₃O (X̃²E) Above the H – CH₂O Dissociation Threshold by Stimulated Emission Pumping