Vibrational structure, photoelectron spectroscopy studies

Most of what we know about the structure of atoms and molecules has been obtained by studying the interaction of electromagnetic radiation with matter. Line spectra reveal the existence of shells of different energy where electrons are held in atoms. From the study of molecules by means of infrared spectroscopy we obtain information about vibrational and rotational states of molecules. The types of bonds present, the geometry of the molecule, and even bond lengths may be determined in specific cases. The spectroscopic technique known as photoelectron spectroscopy (PES) has been of enormous importance in determining how electrons are bound in molecules. This technique provides direct information on the energies of molecular orbitals in molecules. 

Aluminum forms mixed oxides with many other metals which either replace Al3+ in octahedral positions or occupy tetrahedral sites. The spinel structure of MgAl204, an important prototype, has been investigated by photoelectron spectroscopy.122 Vibrational and solid state NMR methods are also useful for studying aluminate structures.12 125... 

The primary techniques used in this study include X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RAIR), and attenuated total reflectance infrared spectroscopy (ATR). XPS is the most surface-sensitive technique of the three. It provides quantitative information about the elemental composition of near-surface regions (< ca. 50 A sampling depth), but gives the least specific information about chemical structure. RAIR is restricted to the study of thin films on reflective substrates and is ideal for film thicknesses of the order of a few tens of angstroms. As a vibrational spectroscopy, it provides the type of structure-specific information that is difficult to obtain from XPS. The... 

This field has expanded very rapidly in just the last two years with the development of many new experimental techniques. The excitement continues. The nature of these new experimental probes has and will continue to significantly influence the development of the field. The ability to select a specific size cluster ion and study its properties is an important new tool. Photoelectron spectroscopy will provide new insight about the electronic structure of clusters as a function of cluster size. Magnetic deflection and electronic susceptibility experiments on neutral clusters and cluster adducts will also provide important information. Vibrational spectroscopy using a variety of different... 

The simplicity of the structure of phosgene has precipitated many structural and spectroscopic studies. This Chapter summarizes the results of the studies by electron diffraction, microwave and vibrational spectroscopy, nuclear magnetic resonance and nuclear quadrupole resonance spectroscopy, and mass spectrometry. Studies by electronic absorption and emission spectroscopy, and photoelectron spectroscopy, are discussed in Chapter 17. 

Full equilibration of ions at a known temperature in IMS allows measuring temperature-dependent rate constants for structural transitions, from which accurate activation energies and preexponential factors could be determined in an assumption-free manner using Arrhenius plots. In contrast, structural characterization techniques implemented in vacuum, such as various laser spectroscopies (threshold photoionization,photodissociation,or photoelectron spectroscopy ), MS/MS by collisional or other dissociation, or chemical reactivity studies lack a direct ion thermometer. In those methods, ion temperature is estimated as the source temperature (possibly with semiempirical adjustments) or gauged using various indirect thermometers, and vibrationally or electronically hot ions are the ever-... 

Femtosecond photoelectron spectroscopy was employed to study the excitation of trons-stilbene above the isomerization reaction barrier [82]. Apart from the contribution, evidence of a second electronic state was found on the basis of two different transients measured across the photoelectron spectrum. Time-dependent density functional theory calculations on So, Si, S2, and Do, tt ether with simulations of the electron energy distribution, supported the experimental findings for selective photoelectron energies of the So, Si,... electronic states. The photoelectron spectra of trans-stilbene following the excitation with 266 nm laser pulses consisting of a pronounced three-peak structure were subjected to a substantia] broadening, due to the large number of closely spaced vibrational states involved in the excitation scheme. 

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