Investigation of the valence electronic structure of n-butane using (e,2e) spectroscopy

Wen-Ning, Pang; Shang, R. C.; Gao, Junfang; Naifei, Gao; Chen, X.J; Deleuze, Michaël S.

doi:10.1016/s0009-2614(98)01056-2

Cited by 13 publications

(8 citation statements)

References 22 publications

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“…We would like to emphasize once more that, from an energy viewpoint, such an assertion is completely incompatible with a vertical depiction of the 1a 1 ionization process of norbornane in its ground-state wave function and C 2 v equilibrium geometry. A number of GF − or MR-SDCI studies on n -alkanes and cycloalkanes, and the present ADC(3) results (Table ) for the 1a 1 , 1b 1 , 1b 2 and 2a 1 orbitals of norbornane show that, compared with the HF level results, the electronic relaxation effects induced by ionization of an electron out of the innermost C 2s orbitals are always within 3.0 and 3.5 eV. Even when invoking configuration interactions in the cation and dispersion of the 1a 1 ionization intensity into shake-up lines (and by extension, shake-off bands in the limit of an asymptotically complete basis set), it seems therefore impossible that a band at 25 eV, thus at ∼1.5 eV below the vertical double ionization threshold, relates via a vertical single or double ionization process to an orbital (1a 1 ) that is characterized by a one-electron binding energy of 31.5 eV at the HF level.…”

Section: Discussion Of Experimental Resultsmentioning

confidence: 53%

The Band 12 Issue in the Electron Momentum Spectra of Norbornane: A Comparison with Additional Green's Function Calculations and Ultraviolet Photoemission Measurements

et al. 2005

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In continuation of a recent study of the electronic structure of norbornane [J. Chem. Phys., 2004, 121, 10525] by means of electron momentum spectroscopy (EMS), we present Green's Function calculations of the ionization spectrum of this compound at the ADC(3) level using basis sets of varying quality, along with accurate evaluations at the CCSD(T) level of the vertical (26.5 eV) and adiabatic (22.1 eV) double ionization thresholds under C(2v) symmetry. The obtained results are compared with newly recorded ultraviolet photoemission spectra (UPS), up to binding energies of 40 eV. The theoretical predictions are entirely consistent with experiment and indicate that, in a vertical depiction of ionization, shake-up states at binding energies larger than approximately 26.5 eV tend to decay via emission of a second electron in the continuum. A band of s-type symmetry that has been previously seen at approximately 25 eV in the electron impact ionization spectra of norbornane is entirely missing in the UPS measurements and theoretical ADC(3) spectra. With regard to these results and to the time scales characterizing electron-electron interactions in EMS (10(-17) s) as compared with that (10(-13) s) of photon-electron interactions in UPS, and considering the p-type symmetry of the electron momentum distributions for the nearest 1b(1) and 1b(2) orbitals, this additional band can certainly not be due to adiabatic double ionization processes starting from the ground electronic state of norbornane, or to exceptionally strong vibronic coupling interactions between cationic states derived from ionization of the latter orbitals. It is therefore tentatively ascribed to autoionization processes via electronically excited and possibly dissociating states.

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Section: Discussion Of Experimental Resultsmentioning

confidence: 53%

The Band 12 Issue in the Electron Momentum Spectra of Norbornane: A Comparison with Additional Green's Function Calculations and Ultraviolet Photoemission Measurements

et al. 2005

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“…In the case of n -butane, the latter gave evidence for a severe breakdown of the orbital picture of ionization for the innermost 3a g one-electron level,22a which in the spectrum appears as a broad set of shake-up lines centered at about 25 eV, accompanied by a correlation tail extending up to at least 60 eV 22b. Preliminary electron momentum spectroscopy measurements (EMS, also referred to as binary (e,2e) spectroscopy) have confirmed the quasi-exclusive relationship of the spectral features recorded at electron binding energies of ∼24 eV and beyond. These measurements have in turn been analyzed in detail on the sole all-staggered form of n -butane using high-order Green's Function ionization energies and Kohn−Sham Density Functional orbitals derived from large basis set calculations.…”

Section: Introductionmentioning

confidence: 81%

“…Ionization spectra are simulated using as convolution function a Gaussian with a constant FWHM (full width at half the maximum) parameter of 1.7 eV, to approximate the resolution found in the experimental spectra. The (e,2e) spectra and orbital density distributions shown in the sequel are calculated according to a Boltzmann-thermostatistical evaluation of the conformer abundances at room temperature (298 K), in line with the average conditions under which the EMS measurements have been completed. , The entropies as well as the zero-point vibrational energies (Table ) used in this evaluation derive from a population analysis within the RRHO (rigid rotors−harmonic oscillators) approximation, on the basis of B3LYP/6-311++G** structures and vibrational frequencies obtained with GAUSSIAN98 . From these thermodynamical data and Allinger's best estimate (0.62 kcal mol -1 ) for the anti / gauche (internal) energy difference, an anti mole fraction of 0.65 is found at room temperature, in fair agreement with the value (0.62 ± 0.04) inferred from the latest spectroscopic work of Durig and co-workers 6d…”

Section: Computational Detailsmentioning

confidence: 99%

“…Ample studies have demonstrated the efficiency of EMS as a particularly sensitive orbital imaging technique, capable of providing detailed information both on electron binding energies throughout the whole valence region, and on the orbital electron density distributions. − At high electron impact energy, according to the plane wave impulse and the sudden (i.e., target Hartree−Fock [HF] or target Kohn−Sham [KS]) approximations, the one-electron EMS cross sections (i.e., momentum distributions) are given by …”

Section: Introductionmentioning

confidence: 99%

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Probing Molecular Conformations with Electron Momentum Spectroscopy: The Case of n-Butane

et al. 2001

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High-resolution (e,2e) measurements of the valence electronic structure and momentum-space electron density distributions of n-butane have been exhaustively reanalyzed in order to cope with the presence of two stable structures in the gas phase, namely the all-staggered and gauche conformers. The measurements are compared to a series of Boltzmann-weighted simulations based on the momentum-space form of Kohn-Sham (B3LYP) orbital densities, and to ionization spectra obtained from high-level [ADC(3)] one-particle Green's Function calculations. Indubitable improvements in the quality of the simulated (e,2e) ionization spectra and electron momentum profiles are seen when the contributions of the gauche form of n-butane are included. Both the one-electron binding energies and momentum distributions consistently image the distortions and topological changes that molecular orbitals undergo due to torsion of the carbon backbone, and thereby exhibit variations which can be traced experimentally. With regard to the intimate relation of (e,2e) cross sections with orbital densities, electron momentum spectroscopy can therefore be viewed as a very powerful, but up to now largely unexploited, conformational probe. The study also emphasizes the influence of thermal agitation in photoionization experiments of all kind.

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“…26 A preliminary, mainly qualitative, investigation of two (e,2e) ionization spectra of n-butane has been presented in Ref. 27. The previous work on ionization of n-butane comprise HeI spectroscopy by Kimura et al, 28 more extended HeII measurements of Price et al 29 and Pots et al, 30 as well as the XPS study of Pireaux et al 2c These works have mainly been focused on traditional aspects of high-resolution photoelectron spectroscopy and have led to observation and assignment of many ionization levels of n-butane.…”

Section: Introductionmentioning

confidence: 99%

Valence electron momentum spectroscopy of n-butane

Wen-Ning

Gao

Ruan

et al. 2000

The Journal of Chemical Physics

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Articles you may be interested inElectron momentum spectroscopy study of Jahn-Teller effect in cyclopropane J. Chem. Phys. 130, 054302 (2009); 10.1063/1.3068619Study of the molecular structure, ionization spectrum, and electronic wave function of 1,3-butadiene using electron momentum spectroscopy and benchmark Dyson orbital theories An investigation of valence shell orbital momentum profiles of difluoromethane by binary (e,2e) spectroscopyThe valence electronic structure and momentum-space electron density distributions of n-butane have been studied by means of high-resolution (e,2e) electron momentum spectroscopy based on noncoplanar symmetric kinematics. Ionization spectra for the range of binding energies 6 to 32 eV and momenta described by azimuthal angles ϭ0°, 2°, 4°, 6°, 8°, and 10°have been recorded and compared to the results of one-particle Green's function calculations, performed using the third-order algebraic-diagrammatic construction ͓ADC͑3͔͒ approximation and series of basis sets of improving quality. Experimental electron momentum profiles have been determined from a set of 11 measurements and compared to theoretical results. It has been shown that despite the complex structure of the spectral bands and the conformational versatility of n-butane, the experimental electron momentum distributions are accurately described by the momentum-space form of orbital densities obtained from Becke three-parameter Lee-Yang-Parr ͑B3LYP͒ density functional calculations. Significant broadening of the spectral lines and the s-type angular dependence of their intensities above 24 eV have been explained by the breakdown of the one-electron picture of ionization for the 3a g molecular orbital.

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Investigation of the valence electronic structure of n-butane using (e,2e) spectroscopy

Cited by 13 publications

References 22 publications

The Band 12 Issue in the Electron Momentum Spectra of Norbornane: A Comparison with Additional Green's Function Calculations and Ultraviolet Photoemission Measurements

The Band 12 Issue in the Electron Momentum Spectra of Norbornane: A Comparison with Additional Green's Function Calculations and Ultraviolet Photoemission Measurements

Probing Molecular Conformations with Electron Momentum Spectroscopy: The Case of n-Butane

Valence electron momentum spectroscopy of n-butane

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