Photoelectron spectra of some halogenomethanes

Novak, Igor; Cvitaš, Tomislav; Klasinc̆, L.; Güsten, H.

doi:10.1039/f29817702049

Cited by 48 publications

(82 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…9 These VIE values are in excellent agreement with He (I) and (II) photoelectron spectra 8,9 and, to a lesser extent, calculations of molecular orbital binding energies using ab initio methods. 10 The first four bands correspond to ionization from chlorine 3pπ lone pair orbitals, with the fifth band (ionization to ) corresponding to removal of a C-Cl σ-bonding electron.…”

Section: Threshold Photoelectron Spectrumsupporting

confidence: 68%

“…These values are in good agreement with those obtained from ab initio studies 10,11 and in excellent agreement with non-threshold photoelectron studies. 8,9 The ground and first excited states are assigned as the chlorine 3pπ lone pair orbitals, which possess 94 and 95% Cl 3p character, respectively. 10 The…”

Section: Chclf 2 421 Threshold Photoelectron Spectrummentioning

confidence: 99%

“…7 By contrast, there is currently a dearth of experimental data on CH 2 ClF. All three molecules have been investigated using non-threshold He (I) and (II) photoelectron spectroscopy 8,9 and by recent ab initio molecular orbital calculations. 10,11 In this study we present an extension to previous work on these three HCFCs by recording the threshold photoelectron spectrum (TPES) and threshold photoelectron-photoion coincidence spectrum (TPEPICO) for each molecule, using synchrotron radiation as the tunable VUV photon source.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Threshold photoelectron–photoion coincidence spectroscopy study of CHCl2F+, CHClF+2 and CH2ClF+: Steric influence of the chlorine, fluorine and hydrogen atoms

Howle

Collins

Tuckett

et al. 2005

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Section: Threshold Photoelectron Spectrumsupporting

confidence: 68%

Section: Chclf 2 421 Threshold Photoelectron Spectrummentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Threshold photoelectron–photoion coincidence spectroscopy study of CHCl2F+, CHClF+2 and CH2ClF+: Steric influence of the chlorine, fluorine and hydrogen atoms

Howle

Collins

Tuckett

et al. 2005

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

“…10 upper spectrum 27 measured ionisation energies by He I photoelectron spectroscopy which were used to assign the Rydberg transitions observed in the absorption spectrum (Table VI). In contrast to CCl 3 Br, 49 no spin-orbit splitting was observed in the He I spectrum since all the states of the parent ion of CF 2 Br 2 are orbitally singly degenerate. The highest-lying molecular orbitals of CF 2 Br 2 are dominated by bromine lone-pair character, so that the lower-energy transitions in the absorption spectrum have associated quantum defects which are close to the values calculated for an isolated bromine atom (ns = 2.96, np = 2.51, nd = 1.10) (see Table VI).…”

Section: Ivc Cf 2 Brmentioning

confidence: 86%

Vacuum–ultraviolet absorption and fluorescence spectroscopy of CF2H2, CF2Cl2, and CF2Br2 in the range 8–22 eV

Seccombe

Chim

Tuckett

et al. 2001

The Journal of Chemical Physics

View full text Add to dashboard Cite

The vacuum-UV absorption and fluorescence spectroscopy of CF 2 X 2 (X=H,Cl,Br) in the range nm is reported. Tunable vacuum-UV radiation in the range 8-22 eV from synchrotron sources at either Daresbury, UK or BESSY1, Germany is used to excite the titled molecules. Fluorescence excitation spectra, with undispersed detection of the fluorescence, were recorded at Daresbury with a resolution of 0.1 nm. VUV absorption spectra at a resolution of 0.08 nm, and dispersed emission spectra with an optical resolution of 8 nm were recorded at BESSY1. Action spectra, in which the VUV energy is scanned with detection of the fluorescence at a specific wavelength, were also recorded at BESSY1 with a resolution of 0.3 nm ; appearance energies for production of a particular emitting state of a fragment are then obtained. Using the single-bunch mode of BESSY1, lifetimes of all emitting states that fall in the range ca. 3-80 ns have been measured. The peaks in the VUV absorption spectra of CF 2 X 2 are assigned to Rydberg transitions. For CF 2 H 2 below 11 eV, there is good agreement between the absorption and the fluorescence excitation spectra, whereas above 11 eV and for the whole range 8-22 eV for CF 2 Cl 2 and CF 2 Br 2 there is little similarity. This suggests that photodissociation to emitting states of fragment species represent minor channels. In the range 8-15 eV, emission is due mainly to CF 2 Ã 1 B 1 − X 1 A 1 and weakly to CFX Ã 1 A" − X 1 A'. These products form by photodissociation of Rydberg states of CF 2 X 2 , and the thresholds for their production therefore relate to energies of the Rydberg states of the parent molecule. For CF 2 H 2 below 11.8 eV CF 2 Ã 1 B 1 can only form with H 2 , whereas for CF 2 Cl 2 and CF 2 Br 2 it is not possible to say whether the other products are 2X or X 2 . For energies above ca. 15 eV, emission is due to diatomic fragments ; CF B 2 ∆ and A 2 Σ + , CCl A 2 ∆, CH B 2 Σ -and A 2 ∆, Cl 2 and Br 2 D' 2 3 Π g , and possibly CBr A 2 ∆. From their appearance energies, there is evidence that, with the exception of CF B 2 ∆ / CF 2 H 2 where the ground state of HF must form , the excited state of CF, CCl or CH forms in association with three atoms. Our results yield no information whether the three bonds in CF 2 X 2 * break simultaneously or sequentially. We suggest that the anomalous behaviour of CF 2 H 2 , in forming H-H or H-F bonds in unimolecular photofragmentation processes, relates to the small size of the hydrogen atom, and hence the unimportance of steric effects in the tightlyconstrained transition state. In no cases is emission observed from excited states of either the CF 2 X free radical or the parent molecular ion, CF 2 X 2 + .4

show abstract

“…Second, the nature of indirect ionisation processes such as autoionisation to produce zero-energy electrons may be probed. The He(I) PES of CCl 3 F, [24][25][26] CCl 3 H, [27,28] and CCl 3 Br [29] have all been measured previously but, to our knowledge, no previous photoelectron spectra under threshold energy conditions have been recorded.…”

Section: Introductionmentioning

confidence: 99%

The use of threshold photoelectron–photoion coincidence spectroscopy to probe the spectroscopic and dynamic properties of the valence states of CCl3F+, CCl3H+ and CCl3Br+

Seccombe

Chim

Jarvis

et al. 2000

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

___________________________________________________________________________Using tunable vacuum-UV radiation from a synchrotron source in the range 10-25 eV, threshold photoelectron -photoion coincidence (TPEPICO) spectroscopy has been used to determine the decay pathways of the valence electronic states of CCl 3 X + (X = F,H,Br). TPEPICO spectra are recorded continuously as a function of photon energy, allowing threshold photoelectron spectra and yields of the fragment ions to be obtained. At fixed photon energies, spectra are also recorded with improved time resolution, allowing total mean translational kinetic energy releases, t , into some dissociation channels to be determined. By comparing t values for single bond-fission processes (i.e. cleavage of a C−Cl or C−X bond) with those predicted for the limiting extremes of a statistical and an impulsive dissociation, information on the nature of the photodissociation dynamics can be inferred. Excited states of all three parent cations show evidence for isolated-state behaviour, and the t values suggest a relationship between the part of the molecule where ionisation occurs and the bond that breaks to form daughter ion + neutral atom products ; impulsive values of t are more likely to be obtained when the breaking bond lies close to the part of the molecule where ionisation occurs, statistical values when ionisation occurs further away from the breaking bond. At higher photon energies, smaller fragment ions are formed following cleavage of more than one bond. With CCl 3 F and CCl 3 Br, the appearance energies of the daughter ions are close to the thermochemical energy for production of that ion with isolated neutral atoms, suggesting strongly that these ions form by bond-fission processes only. With CCl 3 H, at certain energies some fragment ions can only form with molecular neutral fragments (e.g. CCl 2 + + HCl), involving bond-breaking and bond-making processes. It is suggested that this phenomenon is related to the small size of the hydrogen atom, and hence less steric hindrance in a tightly-constrained transition state along the reaction coordinate.

show abstract

Photoelectron spectra of some halogenomethanes

Cited by 48 publications

References 0 publications

Threshold photoelectron–photoion coincidence spectroscopy study of CHCl2F+, CHClF+2 and CH2ClF+: Steric influence of the chlorine, fluorine and hydrogen atoms

Threshold photoelectron–photoion coincidence spectroscopy study of CHCl2F+, CHClF+2 and CH2ClF+: Steric influence of the chlorine, fluorine and hydrogen atoms

Vacuum–ultraviolet absorption and fluorescence spectroscopy of CF2H2, CF2Cl2, and CF2Br2 in the range 8–22 eV

The use of threshold photoelectron–photoion coincidence spectroscopy to probe the spectroscopic and dynamic properties of the valence states of CCl3F+, CCl3H+ and CCl3Br+

Contact Info

Product

Resources

About