INNER SHELL RESONANCES IN PHOTOABSORPTION SPECTRA OF GAS PHASE SILICON COMPOUND MOLECULES

Nous avons mesuré les spectres de photoabsorption des molécules SiX4 (X = H, F, CH3 Cl) dans la région du seuil Si 1s (1840-1900 eV). Des résonances intenses sont observées dans les parties discrètes et continues du spectre. L'interprétation est faite sur la base des propriétés électroniques et structurales des espèces "à coeur équivalent" : les radicaux phosphoranyles PX4 et aussi en termes de résonances de forme.Photoabsorption spectra of SiX4 molecules (X = H, F, CH3 and Cl) have been measured near the Si 1s edge (1840-1900 eV energy range). Intense resonances are observed in the discrete and the continuum part of the spectra. They are interpreted using electronic and structural properties of the core equivalent phosphoranyl radicals PX4 and also in terms of shape resonances

Inner and valence shell electronic excitation of dimethyl sulfoxide by electron energy loss and photoabsorption spectroscopies

The electronic excitation spectra of all inner shells and the valence shell of dimethyl sulfoxide (DMSO) have been measured using electron energy loss spectroscopy (S 2s, 2p, O 1s, C 1s and valence shell) and synchrotron radiation photoabsorption (S 1s). The spectra in the pre-edge regions are interpreted as excitations to virtual valence and Rydberg orbitals. A linear correlation between the SC bond lengths and the term values of S 2p 3 2 → σ* (SC) transitions is demonstrated for DMSO and other sulfur compounds. © 1988.link_to_subscribed_fulltex

RESONANCES IN THE PHOTOABSORPTION SPECTRUM OF THE SILICON TETRACHLORIDE MOLECULE NEAR THE SiK AND ClK EDGES

Le spectre de photoabsorption de SiCl4 en phase gaseuze a été mesuré à l'aide de la méthode du rendement total d'ionisation, près du seuil K du chlore (région 2800-3100 eV). Nous interprétons les résonances près du seuil en comparant ces spectres avec ceux obtenus près du seuil SiK et sur la base de deux calculs indépendants : un basé sur une méthode ab-initio avec interaction de configuration l'autre sur la méthode de diffusion multiple (MSMXα), les deux étant appliqués à la molecule avec coeur équivalent.Photoabsorption spectra of gas phase SiCl4 molecule has been measured using the total ionization yield method, near the chlorine K edge (2800-3100 eV region). We interpret the near edge resonances by comparing the spectra with those obtained near the SiK edge, and on the basis of two independent calculations : ab-initio CI calculations and Multiple Scattering model calculations (MSMXα), both applied to the core equivalent species

Double core vacancy states in X-Ray photoabsorption spectra of gas phase sulfur molecules

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : RM 1550 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

EXAFS studies of the trapping site structure for molecules isolated in cryogenic matrices

We present here results concerning the first attempt of determining the trapping site structure of molecules isolated in inert matrices at low temperature by the EXAFS (Extended X-ray Absorption Fine Structure) method. The experiments have been performed at the K edge of argon, silicon, sulfur, and chlorine for pure solid argon, and for SiH4, OCS and HCl isolated in different cryogenic matrices. The EXAFS technique is sensitive to the local environment around the absorbing atom and the spectral features induced by the matrix material (Ar, Xe, N₂ and CH₄) are clearly evidenced here. The data allow a characterization of the double substitutional site for OCS in argon and xenon while no structure can be determined for the accommodation of SiH₄ in argon. A discussion of the best choice for the guest/host system to obtain a good EXAFS signal is included