Fragmentation of formaldehyde molecular cations

Bombach, Rolf; Dannacher, Josef; Stadelmann, Jean-Pierre; Vogt, J.

doi:10.1016/0020-7381(81)80092-7

Cited by 24 publications

(18 citation statements)

References 14 publications

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“…A minor formation of H + , representing 0.1%, was nevertheless observed in agreement with the experimental threshold for the HCO + H + channel reported at 17.41 eV. 8,13 The electron-ion kinetic energy correlation diagrams (KECD), i.e. the number of events as a function of the ion kinetic energy release (KER) and the photoelectron energy (E e ), for the three DPI channels, (HCO + , e − ), (CO + , e − ) and (H + 2 , e − ) coincident events following excitation at 17 eV are presented in Figure 1 along with the corresponding photoelectron spectra, which are compared to the HeIα photoelectron spectrum reported by Carlsson-Göthe and Karlsson.…”

Section: Resultssupporting

confidence: 88%

“…The fourth H 2 CO + electronic state named C 2 B 1 , is then equivalent to the C 2 B 2 label in previous experimental photoelectron spectra. 13,15,16 A fifth electronic state, D 2 B 2 , not reported experimentally, also resulted from the calculations in agreement with Ref. 18 .…”

Section: Resultssupporting

confidence: 87%

“…This new mechanism bypasses completely the conventional saddle point transition state: the incipient hydrogen atom orbits the remaining part of the molecule until a reactive site is encountered and H 2 + CO are produced by intramolecular abstraction. In contrast, its photoionization and dissociative photoionization (DPI) has been less actively investigated [8][9][10][11][12][13][14][15][16][17][18] . From an experimental point of view, the ionization potentials and fragment appearance thresholds have been reported and different autoionizing ns and np Rydberg series converging to the first and second excited states of H 2 CO + have been identified 9 .…”

Section: Introductionmentioning

confidence: 99%

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Signature of a conical intersection in the dissociative photoionization of formaldehyde

Zanchet

Garcia

Nahon

et al. 2020

Phys. Chem. Chem. Phys.

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Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Signature of a conical intersection in the dissociative photoionization of formaldehyde

Zanchet

Garcia

Nahon

et al. 2020

Phys. Chem. Chem. Phys.

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“…This is also substantiated by the additional data for X' as well as X , ' formation presented in these studies. 34 The reported threshold energies for the formation of these latter species imply that any competitive shift effects are absent. More details on these higher energy decay channels must be sought in the original publication^.^^ quent decay processes.…”

Section: J Dannachermentioning

confidence: 95%

The study of ionic fragmentation by photoelectron‐photoion coincidence spectroscopy

Dannacher

1984

Org. Mass Spectrom.

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S i n c e its invention, a decade ago, photoelectron-photoion coincidence spectroscopy has continuously provided extremely important information on ionic fragmentation processes. The outstanding reputation of the technique is essentially founded on the fact that internal energy selected cations can be studied. In striking contrast to the importance of the method and to the reliability of the data obtained, only about 150 coincidence studies have been published up to now. This is due to the rather intricate experimental technique involved and, probably even more, to the main drawback of this method, i.e. the enormous length of time involved in the measurements. The systems investigated so far are comprehensively compiled in the present article. The two experimental variants currently in use, termed 6xed and variable wavelength technique, are compared. Evidence for the complementary character of the two experimental versions is presented. It is recalled that the primary source of information is in any case a time-of-tlight distribution. The different ways of analysing these distributions are summarized and the accuracy of the derived results is discussed. The current state of the art is exemplilied by reviewing the outcomes for a number of selected examples. The presented results on di-, tri-and tetra-atomic cations reveal clearly the more recently achieved experimental progress. Data on such smaller ionic species are particularly useful for studying predissociation mechanisms, a domain which becomes more and more accessible to modern ab initio calculations of fragmentation pathways. The reported results for 4 ' and COz' reveal that branching ratios for the formation of electronically and viirationally excited dissoeiption products can now be quantified for soffieiently small systems. The possibility of distinct behaviour of isoenergetic molecular ions depending on the method of preparation is outlined in the case of formaldehyde cation. The same cation is used to exemplify a puzzling isotope effect originating in a rate-determining radiationless transition that precedes a significantly faster dissociative step. A variety of data on larger systems grouped according to topic are critically reviewed. The determination and accmcy of rate-energy functions is discussed, at first for the case of a single decay channeb then the analogous analysis for a series of competing fragmentations is outlined. The importance of competitive radiative and non-radiative/dissociative depletion of an excited electronic state is pointed out.

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“…Photodissociation and dissociative ionization of the H 2 CO molecule has been extensively studied experimentally and theoretically. [74][75][76][77][78][79][80][81][82][83][84][85][86][87] There are two low-energy dissociation channels for the cation, producing HCO ϩ and CO ϩ with appearance thresholds of 11.97 eV ͑Ref. 81͒ and 14.10 eV, 37 respectively.…”

Section: Ion Photofragmentationmentioning

confidence: 99%

Multiphoton ionization and photoelectron spectroscopy of formaldehyde via its 3p Rydberg states

Kim

Anderson

2001

The Journal of Chemical Physics

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The resonance-enhanced multiphoton ionization ͑REMPI͒ spectrum of formaldehyde, two photon resonant in the region of the 1 A 2 (3p x), 1 A 1 (3p y), and 1 B 2 (3p z) states, is reported. The 1 A 2 (3p x) state spectrum is dominated by the 3 Ј ͑CH 2 scissors͒, 4 Ј ͑CH 2 out-of-plane bending͒, 5 Ј ͑CH 2 asymmetric stretching͒, and 6 Ј ͑CH 2 rock͒ modes, with weaker bands observed for excitation of the 2 Ј ͑CO stretching͒ mode. Vibrational analysis of the spectrum provides many new frequencies for the 1 A 2 (3p x) state, not resolved or accessible in single photon spectroscopic measurements. Photoelectron spectroscopy is used to probe the nature of the vibronic levels associated with the 1 A 2 (3p x) intermediate state, to measure vibrational frequencies of the resulting cations, and to identify useful routes for preparing vibrational state-selected H 2 CO ϩ. It is found that H 2 CO͓ 1 A 2 (3p x)͔ is a well-behaved Rydberg state, generating cations in the same vibrational level that was populated in the intermediate. Cations with mode-selective excitation of up to 0.62 eV can be produced. Ab initio calculations are used to help assign the cation vibrations. In contrast to the well-behaved 1 A 2 (3p x) state, the 1 A 1 (3p y) and 1 B 2 (3p z) states are strongly mixed with each other and with valence states.

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Fragmentation of formaldehyde molecular cations

Cited by 24 publications

References 14 publications

Signature of a conical intersection in the dissociative photoionization of formaldehyde

Signature of a conical intersection in the dissociative photoionization of formaldehyde

The study of ionic fragmentation by photoelectron‐photoion coincidence spectroscopy

Multiphoton ionization and photoelectron spectroscopy of formaldehyde via its 3p Rydberg states

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