Electronic Structure of Benzene Studied in USX Emission

Nordgren, Joseph; Selander, L; Pettersson, L; Brammer, R.; Bäckström, Mikael; Nordling, C.; Ågren, Hans

doi:10.1088/0031-8949/27/3/004

“…For weakly interacting molecules it is known that the major effect of condensation is a uniform shift of all spectral features, while the overall spectral shape is preserved. [16] The observations are fully consistent with the notion that the water molecules in the low-concentration solution interact only weakly with the surroundings. At increasing water concentration the interaction increases, and the changes in the spectra can be unambiguously assigned to this interaction.…”

supporting

confidence: 83%

On the Origin of the Hydrogen‐Bond‐Network Nature of Water: X‐Ray Absorption and Emission Spectra of Water–Acetonitrile Mixtures

Lange

¹

,

Könnecke

²

,

Soldatov

³

et al. 2011

View full text Add to dashboard Cite

Liquid water plays a significant role, especially as a solvent in the fields of biology and biochemistry. Its strong impact on protein function and activity in the direct surrounding of proteins led to the coining of the term biological water. [1] Investigations of the hydration of polar and nonpolar protein sites, or of systems which can mimic this interaction, such as mixtures of water with solvents of different polarity, are of great interest. However, even for pure liquid water the complex nature of the hydrogen-bond (HB) network is still in the course of clarification. One open question in this context is whether in the dynamic bond-building and -breaking equilibrium of liquid water a continuum of almost tetrahedral bond configurations [2] or rather a number of distinct preferential species of broken and unbroken HB configurations exists.[3] X-ray absorption (XA) and X-ray emission (XE) spectroscopy, which reveal information about the local electronic structure, have been used to pursue this question. [3b, 4] In XA spectroscopy a core electron is excited to the unoccupied states of a molecule, and thus probes the corresponding local electronic structure. The oxygen K-edge XA spectrum of liquid water shows three main features: a pre-edge at 535 eV, a main edge around 537 eV and a postedge around 540 eV. Isotope-, temperature-, and phasedependent measurements on water in combination with theoretical simulations led to the proposal that these features are correlated to distinct HB conformations: the post-edge to tetrahedrally bonded water molecules and the pre-and main edges to conformations with broken HBs. [3,5] This interpretation indicated that a significant number of water molecules with only one strong donating and one strong accepting HB is present in the liquid phase, challenging the traditional tetrahedral model. This new interpretation has been questioned, and based on theoretical modeling it has been argued that XA spectra are rather insensitive to the HB network.[6] X-ray emission spectroscopy probes the occupied electronic states on detecting the energy distribution of the radiative decay of the core-hole state. The recent development of high-resolution XE spectrometers for liquid samples drew particular attention to the observation of the splitting of the sharpest peak in the spectrum associated with the lonepair orbital of the free water molecule.[4a,f,g] Tokushima et al. interpreted the double feature as further proof for the existence of two different structures, the tetrahedral and strongly distorted H-bonded species.[4g] Fuchs et al. assign the two distinct peaks to emission from species before and after core-hole-induced ultrafast dissociation.[4a] Experimental approaches to clarify the origin of the peak splitting included temperature-, isotope-, and state-of-aggregation-dependent measurements, as well as the study of the proposed dissociated species.To shed further light on this issue we present XA and XE spectra of the water molecule in a chemical environment in which the HB configura...

show abstract

“…Neglecting differences in excitation dynamics between direct photoemission and XE, we would thus expect a low‐energy shift of the 1b 1 ‐derived feature of 0.52 eV, whereas a direct measurement4g gives a low‐energy shift of around 0.3 eV if the d 1 feature is identified with the 1b 1 hole state. For weakly interacting molecules it is known that the major effect of condensation is a uniform shift of all spectral features, while the overall spectral shape is preserved 16. The observations are fully consistent with the notion that the water molecules in the low‐concentration solution interact only weakly with the surroundings.…”

supporting

confidence: 81%

On the Origin of the Hydrogen‐Bond‐Network Nature of Water: X‐Ray Absorption and Emission Spectra of Water–Acetonitrile Mixtures

Lange

¹

,

Könnecke

²

,

Soldatov

³

et al. 2011

View full text Add to dashboard Cite

Liquid water plays a significant role, especially as a solvent in the fields of biology and biochemistry. Its strong impact on protein function and activity in the direct surrounding of proteins led to the coining of the term biological water. [1] Investigations of the hydration of polar and nonpolar protein sites, or of systems which can mimic this interaction, such as mixtures of water with solvents of different polarity, are of great interest. However, even for pure liquid water the complex nature of the hydrogen-bond (HB) network is still in the course of clarification. One open question in this context is whether in the dynamic bond-building and -breaking equilibrium of liquid water a continuum of almost tetrahedral bond configurations [2] or rather a number of distinct preferential species of broken and unbroken HB configurations exists.[3] X-ray absorption (XA) and X-ray emission (XE) spectroscopy, which reveal information about the local electronic structure, have been used to pursue this question. [3b, 4] In XA spectroscopy a core electron is excited to the unoccupied states of a molecule, and thus probes the corresponding local electronic structure. The oxygen K-edge XA spectrum of liquid water shows three main features: a pre-edge at 535 eV, a main edge around 537 eV and a postedge around 540 eV. Isotope-, temperature-, and phasedependent measurements on water in combination with theoretical simulations led to the proposal that these features are correlated to distinct HB conformations: the post-edge to tetrahedrally bonded water molecules and the pre-and main edges to conformations with broken HBs. [3,5] This interpretation indicated that a significant number of water molecules with only one strong donating and one strong accepting HB is present in the liquid phase, challenging the traditional tetrahedral model. This new interpretation has been questioned, and based on theoretical modeling it has been argued that XA spectra are rather insensitive to the HB network.[6] X-ray emission spectroscopy probes the occupied electronic states on detecting the energy distribution of the radiative decay of the core-hole state. The recent development of high-resolution XE spectrometers for liquid samples drew particular attention to the observation of the splitting of the sharpest peak in the spectrum associated with the lonepair orbital of the free water molecule.[4a,f,g] Tokushima et al. interpreted the double feature as further proof for the existence of two different structures, the tetrahedral and strongly distorted H-bonded species.[4g] Fuchs et al. assign the two distinct peaks to emission from species before and after core-hole-induced ultrafast dissociation.[4a] Experimental approaches to clarify the origin of the peak splitting included temperature-, isotope-, and state-of-aggregation-dependent measurements, as well as the study of the proposed dissociated species.To shed further light on this issue we present XA and XE spectra of the water molecule in a chemical environment in which the HB configura...

show abstract

“…The empirical procedure for obtaining the DOS has been described previously.n.lo It involves the use of x-ray emission (XES) and photoelectron (XPS) spectra, and in some cases theoretical calculations. 2 the experimental line shape for the gas phase molecules is shifted by about (rIO eV to higher two-electron binding energy (or lower Auger kinetic energy). First, most one-electron theoretical calculations do not include electron correlation effects and therefore do not give sufficiently accurate binding energies.…”

Section: Overviewmentioning

confidence: 93%

“…2 The basic processes for C2Ho/Ni are different from that for the others, but they can be related to the gas phase molecular case (e,g., ethylene), 10 The spectrum in Fig. (3) assuming that the sum over I' is limited to the orbital with the resonantly excited electron.…”

Section: B Satellitesmentioning

confidence: 99%

Chemical effects in the carbon K V V Auger line shapes

Ramaker

¹

1989

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

View full text Add to dashboard Cite

A carbon Auger line shape study of nitroaromatic explosives J. Chem. Phys. 80, 4513 (1984); 10.1063/1.447236Auger line shape studies of carbon species on Rh and Ni surfaces J. Vac. Sci. Technol. A 1, 995 (1983); 10.1116/1.572021 C(K V V) Auger line shape of chemisorbed CO Summary Abstract: Evidence for screening effects in the carbon K V V Auger line shape of intercalated graphiteWe review the results of a consistent quantitative interpretation of the C KVV Auger line shapes of five different gas phase hydrocarbons (methane, ethane, cyclohexane, benzene, and ethylene), three solids (polyethylene, diamond, and graphite), and a molecularly chemisorbed system (ethylene/Ni). The normal kvv line shape accounts for only about one-half of the total experimental intensity for most of the Auger line shapes. The remaining part of the experimental line shape can be attributed to satellites resulting from resonant excitation or dynamic screening processes. The normal kut' Auger line shapes are seen to reflect delocalized holes; however, correlation effects are very evident. Although these screening and correlation effects complicate the interpretation of the line shapes, they provided a means to obtain unique chemical, electronic, and bonding information, and indeed cause the principal differences seen among the experimental line shapes.

show abstract

Electronic Structure of Benzene Studied in USX Emission

Cited by 24 publications

References 21 publications

On the Origin of the Hydrogen‐Bond‐Network Nature of Water: X‐Ray Absorption and Emission Spectra of Water–Acetonitrile Mixtures

On the Origin of the Hydrogen‐Bond‐Network Nature of Water: X‐Ray Absorption and Emission Spectra of Water–Acetonitrile Mixtures

On the Origin of the Hydrogen‐Bond‐Network Nature of Water: X‐Ray Absorption and Emission Spectra of Water–Acetonitrile Mixtures

Chemical effects in the carbon K V V Auger line shapes

Contact Info

Product

Resources

About