An experimental and theoretical study of the valence shell photoelectron spectrum of tetrafluoromethane (original) (raw)
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Journal of Physics B: Atomic, Molecular and Optical Physics, 2014
The threshold photoelectron spectra (TPES) of the two vicinal isomers of the 1,2-C 2 H 2 FCl molecule have been investigated in the 9-24 eV energy range using synchrotron radiation. Eight (for the cis-isomer) or nine (for the trans-isomer) bands have been observed and the corresponding ionization energies have been determined. The spectroscopic assignments are based on high level quantum chemical αb initio calculations for both isomers. Most of the observed spectral features could be interpreted. For both species the first three TPES bands exhibit a rich vibrational structure. Vibrational energies were determined and assignments were also supported by quantum chemical calculations of vibrational wavenumbers for these three ionic states of both isomers.
Valence electronic structure and photofragmentation of 1,1,1,2-tetrafluoroethane (CF3-CH2F)
Physical Review A, 2012
The electronic structure and fragmentation of the hydrofluorocarbon compound 1,1,1,2-tetrafluoroethane (CF 3-CH 2 F) were studied using spectroscopical methods and quantum chemical calculations. Valence photoelectron spectra and the ionic fragmentation products were recorded with synchrotron radiation in the vacuum ultraviolet (VUV) region. The geometric and electronic structures of the CF 3-CH 2 F molecule were calculated using the complete active space perturbation theory of second order. The calculated vertical ionization energies were used to interpret the experimental photoelectron spectrum. VUV photodissociation of the sample molecule was studied with photoelectron-photoion coincidence spectroscopy. Coincident ion yields are shown for several cations as a function of electron binding energy. The experimental data are discussed in comparison with theory and previous work.
Chemical Physics Letters, 2017
Photoelectron spectra of a-tetrahydrofurfuryl alcohol (THFA) molecules, the threshold spectrum and spectra for constant photoelectron energies, have been measured over the photon energy range 9-25 eV. Analysis of the photoelectron spectra has allowed overlapping photoionization bands to be separated, tentatively assigned and their vertical photoionization energies to be determined. These energies are compared with existing theoretical calculations. The photoelectron spectra indicate the predominance of one conformer in the population of gas-phase THFA.
High resolution photoelectron spectroscopy of bromochlorofluoromethane
Molecular Physics, 1996
High resolution He1 (580A) photoelectron spectra of As,, As,, and P4 were obtained with a newly-built high temperature molecular beam source. Vibrational structure was resolved in the photoelectron spectra of the three cluster species. The Jahn-Teller effect is discussed for the ' E and T2 states of P: and As:. As a result of the Jahn-Teller effect, the ' E state splits into two bands, and the ,T2 state splits into three bands, in combination with the spin-orbit effect. It was observed that the v2 normal vibrational mode was involved in the vibronic interaction of the ,E state, while both the v2 and v, modes were active in the * T, state.
Journal of Physics Communications, 2017
This work analyzes the threshold photoelectron spectrum (TPES) and selected constant ion state (CIS) spectra of the 1,1-C 2 H 2 Cl 2 isomer measured using synchrotron radiation. The TPES is compared to the HeI-, NeI-and ArII-photoelectron spectra (PES). In the HeI-PES nine photoelectron bands have been observed at vertical ionization energies of 9.992 eV, 11.652 eV, 12.157 eV, 12.536 eV, 13.633 eV, 14.195 eV, at about 15.9 eV and 16.2 eV and at 18.496 eV successively. For most of these bands the adiabatic ionization energy could be determined and a detailed vibrational analysis of the first four bands is presented. All these bands exhibit an extended vibrational structure. In particular, the ground electronic state and the third excited state display an extended vibrational structure upon excitation by the ArII-resonance line. The assignments of the electronic bands and of the vibrational structure are based on quantum chemical calculations. These allowed us to assign the nine electronic states in terms of ionization and double excitation in a molecular orbital scheme. The good correlation between predicted vibrational wavenumbers and the experimental values allowed us to assign all observed vibrational structures. The CIS spectrum of the eight first electronic states of +-1, 1 C H Cl 2 2 2 have also been recorded. Vibrationally resolved CIS spectra of the molecular ion ground state have been obtained and are discussed.
Journal of the American Chemical Society, 1976
The photoelectron spectra (He(1) and He(I1)) of a series of cycloalkenes (c3-C~) and methylenecycloalkenes (C3-C,) are presented along with those of related open chain compounds. The calculated MO energies using a 4-31G basis set are also given. A good correlation between ionization potentials and MO energies was found, but the correlation did not have a zero intercept. The correlation was useful in assigning the bands in the photoelectron spectra of the larger molecules for which overlapping bands could not experimentally be resolved and suggests a relationship between the neutral molecule MO energy and the sum of the correlation and reorganization energies on going to the ion.
The Journal of Physical Chemistry, 1995
The title reactions have been investigated in the gas phase using UV photoelectron spectroscopy. By recording spectra at different reaction times, it was possible to detect reaction intermediates and hence identify pathways by which each reaction proceeds. The F2 + CH3SCH3 reaction appears to proceed via the intermediate CH3-SFCH3 whereas the F2 + CH3SSCH3 reaction gives H2CS and HF as the first observed products. For both reactions at longer reaction times, a new spectrum associated with a reaction product, consisting of three photoelectron bands with adiabatic ionization energies of 10.15 f 0.01, 11.49 f 0.02, and 13.71 0.01 eV, has been observed. This spectrum is assigned to the HFCS molecule. The first two adiabatic ionization energies of HFCS have been calculated using the Gaussian-2 (G2) theoretical procedure as 10.09 and 1 1.5 1 eV, respectively, supporting this assignment. This work represents the first observation and spectroscopic study of this molecule. A broad band with a vertical ionization energy of 10.58 f 0.06 eV, assigned to the first ionization energy of HCF, has also been observed as a secondary product from both reactions under conditions of excess F2 partial pressure. This assignment is supported by first adiabatic and vertical ionization energies of HCF computed at the G2 level of theory. For each reaction, a reaction mechanism is proposed on the basis of the results obtained.
Multimode Jahn–Teller and pseudo-Jahn–Teller coupling effects in the photoelectron spectrum of CH3F
Chemical Physics, 2004
The multimode Jahn-Teller (JT) and pseudo-Jahn-Teller (PJT) coupling effects in the photoelectron spectrum of methylfluoride are theoretically investigated with the aid of an ab initio quantum dynamical approach. The theoretical findings are compared with the experimental results of Karlsson et al. [Phys. Scripta 16 (1977) 225]. At the vertical configuration, the ground, first and second excited electronic states of the methylfluoride radical cation belong to the 2 E, 2 A 1 and 2 E symmetry species. The three doubly degenerate vibrational modes cause a splitting of the degeneracy of the E electronic states of the radical cation and exhibit the (E e)-JT effect. The same vibrational modes may also cause a coupling of the degenerate and the non-degenerate electronic states (PJT effect). In our theoretical approach we devise a model diabatic vibronic Hamiltonian within a quadratic vibronic coupling scheme. The parameters of the Hamiltonian are derived by performing extensive ab initio calculations at the CASSCF-MR-AQCC level of theory. The photoelectron bands are calculated by a quantum dynamical approach based on the Lanczos algorithm. A detailed examination of the various static and dynamic aspects of the problem reveals an interesting interplay of JT and PJT coupling effects in the photoelectron-induced dynamics of CH 3 F þ . The resolved progression in the first photoelectron band corresponding to the groundX 2 E electronic manifold of CH 3 F þ is found to be mainly caused by the C-F stretching (a 1 ), C-F bending (e) and CH 3 deformation (e) modes. The JT coupling effects are not particularly strong in this electronic manifold. This also holds for the second photoelectron band attributed to the vibronic structure of theà 2 A 1 andB 2 E electronic states of CH 3 F þ . However, the extremely large Condon activity of the symmetric vibrational modes in theà 2 A 1 electronic state contributes much to the broad and highly diffuse nature of this band which is also observed experimentally. The PJT activity of the anti-symmetric C-F bending (e) vibration in theX 2 E andB 2 E electronic states is also discussed.
Photoelectron spectra of molecules. Part 12. Vinyl, allyl, and phenyl ethers and sulphides
2002
He I (21.21 eV) photoelectron spectra of 21 vinyl, allyl, and phenyl ethers and sulphides are The main goal of this treatment was to compare the structural effects in two closely related classes of compounds: oxygencontaining vinyl compounds and analogous ones containing sulfur. To clarify the various aspects of the substituent effects on the behavior of ionization centers in the gas phase, some chlorosubstituted compounds are included. The photoelectron spectra have been recorded and analyzed on the basis of correlation with the spectra of related compounds for which assignments are established. Ab initio quantum chemical calculations with a complete optimization of the geometry were accomplished for interpretation of the spectra as well. The Gaussian-98 system of programs was applied using 6-31G* basis set. For comparison, the density functional theory (DFT) using the B3LYP hybride functional and a 6-31G* basis set was also employed. q Journal of Molecular Structure (Theochem) 579 (2002) 205±220 0166-1280/02/$ -see front matter q