Photoionization of formaldehyde

Praet, M.-Th.; Delwiche, J.

doi:10.1016/0020-7381(68)85009-0

Cited by 14 publications

(14 citation statements)

References 13 publications

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“…Specifically, bounding approximations are constructed to the cumulative oscillator-strength distribution, and these are differentiated in the S-T sense with respect to the energy variable. 3 s, 37 The oscillator-strength density so obtained exhibits resonancelike structures at the appropriate discrete transition frequencies, and is smooth in the photoionization region. 32 -39 The strengths of the discrete transitions are obtained by constructing the so-called Stieltjes histogram, which provides a generalization of the familiar Coulomb extrapolation at the ionization limit.…”

Section: =1mentioning

confidence: 87%

“…41 • 42 Moreover, in computational applications, the recurrence coefficients (5) for the polynomials orthogonal with respect to the oscillator-strength density are calculated directly from the primitive spectrum of Eq. (1) employing a stable computational algorithm, 3 5, 36 avoiding explicit solution of Eq. (4).…”

Section: =1mentioning

confidence: 99%

“…The moment-theory spectrum [Eq. (3)] is then obtained from the poles and residues of appropriately defined orthogonal-polynomial rational fractions. 37 The recurrence coefficients of Eq.…”

Section: =1mentioning

confidence: 99%

“…[2][3][4][5][6] warrant additional discussion. In order to clarify their natures, the spatial distributions of the final-state resonance orbitals in each case can be unambiguously established by examining the pseudospectral functions contained in the appropriate excitation-energy interval.…”

Section: B Photoionization Resonancesmentioning

confidence: 99%

“…In the present report, it is sufficient to infer and describe the natures of the final-state resonance orbitals qualitatively, making use only of the photoionization cross sections of Figs. [2][3][4][5][6] and an understanding of the virtual orbitals anticipated on basis of valence calculations. 24 • 47 • 51 • 52 In Fig.…”

Section: B Photoionization Resonancesmentioning

confidence: 99%

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Photoabsorption in formaldehyde: Intensities and assignments in the discrete and continuous spectral intervals

Langhoff

Orel

Rescigno

et al. 1978

The Journal of Chemical Physics

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Theoretical investigations of total and partial-channel photoabsorption cross sections in molecular formaldehyde are reported employing the Stieltjes-Tchebycheff (s-T) technique and separated-channel static-exchange (!YO) calculations. Vertical one-electron dipole spectra for the 2b 2 (n), lb 1(7T), 5a 1(a), I b 2 , and 4a 1 canonical molecular orbitals are obtained using Hartree-Fock frozen-core functions and large basis sets of compact and diffuse normalizable Gaussians to describe the photoexcited and ejected electrons. The calculated discrete excitation spectra provide reliable zeroth-order approximations to both valence and Rydberg transitions, and, in particular, the 2b 2 (n)-msa 1 , npa 1 , npb 2 , and nda 2 IVO spectra are in excellent accord with recent experimental assignments and available intensity measurements. Convergent (S-T) photoionization cross sections in the static-exchange (IVO) approximation are obtained for the 15 individual partial channels associated with ionization of the five occupied molecular orbitals considered. Resonance features in many of the individual-channel photoionization cross sections are attributed to contributions frorn valencelike a 1 a*(CO), a 1 a*(CH), and b 2 a*(CH)/7Ty *(CO) molecular orbitals that appear in the photoionization continua, rather than in the corresponding one-electron discrete spectral intervals. The vertical electronic cross sections for 1 A 1 -+ 1 B 1 , 1 B 2 , and 1 A 1 excitations are in generally good accord with previously reported CI (s-T) predictions of continuum orbital assignments and intensities, although some discrepancies due to basis-set differences are present in the 1 B 1 and 1 B 2 components, and larger discrepancies apparently due to channel coupling are present in the 1 A 1 -+ 1 A 1 cross section. Partialchannel vertical electronic cross sections for the production of the five lowest parent-ion electronic states are found to be in general agreement with the results of very recent synchrotron-radiation photoelectron branching-ratio measurements in the 20 to 30 eV excitation energy interval. Most important in this connection is the tentative verification of the predicted orderings in intensities of the partial-channel cross sections, providing support for the presence of a strong ka 1

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Section: =1mentioning

confidence: 87%

Section: =1mentioning

confidence: 99%

“…The moment-theory spectrum [Eq. (3)] is then obtained from the poles and residues of appropriately defined orthogonal-polynomial rational fractions. 37 The recurrence coefficients of Eq.…”

Section: =1mentioning

confidence: 99%

Section: B Photoionization Resonancesmentioning

confidence: 99%

Section: B Photoionization Resonancesmentioning

confidence: 99%

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Photoabsorption in formaldehyde: Intensities and assignments in the discrete and continuous spectral intervals

Langhoff

Orel

Rescigno

et al. 1978

The Journal of Chemical Physics

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Illustrating the Fate of Methyl Radical in Photocatalytic Methane Oxidation over Ag−ZnO by in situ Synchrotron Radiation Photoionization Mass Spectrometry

et al. 2023

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Photocatalysis has emerged as an ideal method for the direct activation and conversion of methane under mild conditions. In this reaction, methyl radical ( * CH 3 ) was deemed a key intermediate that affected the yields and selectivity of the products. However, direct observation of * CH 3 and other intermediates is still challenging. Here, a rectangular photocatalytic reactor coupled with in situ synchrotron radiation photoionization mass spectrometry (SR-PIMS) was developed to detect reactive intermediates within several hundred microseconds during photocatalytic methane oxidation over AgÀ ZnO. Gas phase * CH 3 generated by photogenerated holes (O À ) was directly observed, and its formation was demonstrated to be significantly enhanced by coadsorbed oxygen molecules. Methoxy radical (CH 3 O * ) and formaldehyde (HCHO) were confirmed to be key C1 intermediates in photocatalytic methane overoxidation to CO 2 . The gas-phase selfcoupling reaction of * CH 3 contributes to the formation of ethane, which indicates the key role of * CH 3 desorption in the highly selective synthesis of ethane. Based on the observed intermediates, the reaction network initiated from * CH 3 of photocatalytic methane oxidation could be clearly illustrated, which is helpful for studying the photocatalytic methane conversion processes.

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Illustrating the Fate of Methyl Radical in Photocatalytic Methane Oxidation over Ag−ZnO by in situ Synchrotron Radiation Photoionization Mass Spectrometry

et al. 2023

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Photocatalysis has emerged as an ideal method for the direct activation and conversion of methane under mild conditions. In this reaction, methyl radical (⋅CH3) was deemed a key intermediate that affected the yields and selectivity of the products. However, direct observation of ⋅CH3 and other intermediates is still challenging. Here, a rectangular photocatalytic reactor coupled with in situ synchrotron radiation photoionization mass spectrometry (SR‐PIMS) was developed to detect reactive intermediates within several hundred microseconds during photocatalytic methane oxidation over Ag−ZnO. Gas phase ⋅CH3 generated by photogenerated holes (O−) was directly observed, and its formation was demonstrated to be significantly enhanced by coadsorbed oxygen molecules. Methoxy radical (CH3O⋅) and formaldehyde (HCHO) were confirmed to be key C1 intermediates in photocatalytic methane overoxidation to CO2. The gas‐phase self‐coupling reaction of ⋅CH3 contributes to the formation of ethane, which indicates the key role of ⋅CH3 desorption in the highly selective synthesis of ethane. Based on the observed intermediates, the reaction network initiated from ⋅CH3 of photocatalytic methane oxidation could be clearly illustrated, which is helpful for studying the photocatalytic methane conversion processes.

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Photoionization of formaldehyde

Cited by 14 publications

References 13 publications

Photoabsorption in formaldehyde: Intensities and assignments in the discrete and continuous spectral intervals

Photoabsorption in formaldehyde: Intensities and assignments in the discrete and continuous spectral intervals

Illustrating the Fate of Methyl Radical in Photocatalytic Methane Oxidation over Ag−ZnO by in situ Synchrotron Radiation Photoionization Mass Spectrometry

Illustrating the Fate of Methyl Radical in Photocatalytic Methane Oxidation over Ag−ZnO by in situ Synchrotron Radiation Photoionization Mass Spectrometry

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