X-ray Bremsstrahlung Isochromat Spectroscopy Research Articles

Electronic structure of silicon nitride

The electronic structure of valence and conduction bands of silicon nitride SiN x layer deposited on a silicon substrate was studied using X-ray photoelectron spectroscopy (XPS) and X-ray bremsstrahlung isochromat spectroscopy (BIS), respectively, and compared with the density of states (DOS) taken from the literature. In the isochromat spectrum measured at photon energy 5415 eV, a strong maximum at 9.7 eV and a weak extended structure in the energy range up to 200 eV above the BIS edge were observed. A theoretical calculation of extended X-ray bremsstrahlung isochromat fine structure (EXBIFS) for silicon nitride has been performed using a multiple scattering method and partial probabilities of X-ray bremsstrahlung transitions calculated for continuum states in a dipole approximation. The results have shown that the X-ray bremsstrahlung isochromat fine structure for silicon nitride appears mainly due to electron transitions to the s states localized near Si ions.

Electronic structures of Nd 1−xSr xMnO 3, La 1−xSr xMnO 3 and La 1−x Ca xMnO 3 studied by photoemission and inverse photoemission spectroscopy

We have investigated the electronic structures of perovskite manganese oxides, Nd 0.5Sr 0.5MnO 3, (Nd 0.062Sm 0.938) 0.5Sr 0.5MnO 3, La 0.84Sr 0.16MnO 3 and La 0.7Ca 0.3MnO 3, by X-ray photoemission (XPS) and X-ray bremsstrahlung isochromat spectroscopy in addition to vacuum ultraviolet inverse photoemission. It is found that the VUV-IPES spectra seem to be well explained by the band-structure calculation. Mn 3p-3d resonance photoemission measurements have also been performed, where the contributions of the occupied Mn 3d states are extracted. We observed hybridization between the Mn 3d and O 2p states from the Mn 2p and 3p spectra of all samples, and the Mn spin state from the Mn 3s XPS spectra of Nd 0.5Sr 0.5MnO 3 and (Nd 0.062Sm 0.938) 0.5Sr 0.5MnO 3.

Photoemission and bremsstrahlung isochromat spectra of U3P4 and U3As4.

The electronic structures of ${\mathrm{U}}_{3}$${\mathrm{P}}_{4}$ and ${\mathrm{U}}_{3}$${\mathrm{As}}_{4}$ single crystals are probed by x-ray and vacuum ultraviolet photoemission spectroscopy (XPS and UPS) as well as by x-ray bremsstrahlung isochromat spectroscopy (BIS). The BIS spectra show a broad peak at \ensuremath{\sim}1.8 eV above the Fermi level (${\mathit{E}}_{\mathit{F}}$) with a noticeable tail. Its energy separation of \ensuremath{\sim}2.5 eV from the U 5f UPS peak is larger than ${\mathrm{U}}_{5\mathit{f},5\mathit{f}}$=1.2 eV. This difference is interpreted as mostly due to the spin-orbit splitting of the U 5f state. The U 4f core XPS has shown rather an asymmetric shape with a tail toward larger binding energies (${\mathit{E}}_{\mathit{B}}$). A satellite not directly observable in the experimental spectrum is revealed at \ensuremath{\sim}5.4 eV by deconvolution. Based on an extended Anderson impurity model, it is interpreted as the ``p-d antibonding state.'' The appreciable density of the U 6d state near ${\mathit{E}}_{\mathit{F}}$ strongly influences the photoemission spectra.

Photoemission, Inverse Photoemission and Optical Studies of Rare-Earth Hexaborides

Electronic structures of rare-earth hexaborides (RB 6 ) have been investigated by photoemission and inverse photoemission spectroscopy. The X-ray photoemission (XPS) features of the 3 d and 4 d core states of heavy R elements are interpreted in comparison with the multiplet calculation. The valence band spectra probed by XPS and X-ray bremsstrahlung isochromat spectroscopy (X-BIS) methods are fully utilized to interpret the optical conductivity spectra.

On the possibility of bremsstrahlung—isochromat spectroscopy for gas-phase molecules

Abstract Experimental and theoretical possibilities for X-ray bremsstrahlung—isochromat spectroscopy of gas-phase molecules are considered. It is argued that sufficient bremsstrahlung intensity can be obtained with the use of high-intensity monochromators developed for X-ray photoelectron spectroscopy and with electron optics for gas-phase X-ray emission spectroscope. Transition amplitudes and intensities for the process are formulated using general many-electron wavefunctions for bound states and assuming strong orthogonality between the wavefunction of the incoming electron and the neutral ground state. The role of correlation and relaxation effects is analyzed and analogies to the theory of photoionization utilized in a discussion of possible experimental effects.