Core-exciton induced resonant photoemission in the covalent semiconductor black phosphorus

Valence band photoemission spectra of black phosphorus have shown anomalous behavior at the excitation of 2p core-excitons. The intensity of the 2.7 ev peak shows a clear Fano type interference due to a direct recombination of core-excitons leaving one hole in valence bands. Besides, strong enhancement of the 10.8 eV peak is interpreted as due to a core-exciton induced resonance with two-hole final states. The role of core-excitons as intermediate states for photoemission processes is newly revealed in the experiments.     

Efficient N-sulfenylation of 2-azetidinones using S-substituted thiophthalimides

Reaction of N-unsubstituted β-lactams with various S-substituted thiophthalimides provides an efficient route to the corresponding N-thio-2-azetidinones.     

Ultraviolet photoemission and 4d core reflectance spectra of SmSe(100)

Ultraviolet photoemission (UPS) and inner core reflectance spectra have been measured on SmSe(100) surface with synchrotron radiation. Besides the multiplet structures observed in UPS spectra for the Sm 4f, 5p and 5s excitations, the reflectance spectrum has revealed a multiplet structure associated with the Sm 4d→4f excitation. Each band of the UPS spectra has shown remarkably different hν dependence and the resonant behavior of the cross section. Sm 4f- and Se 4p-derived valence band features are unambiguously identified by the angle resolved UPS.     

Time-resolved ESR study of the lowest excited triplet states of para-quinones in glassy matrices at 77 k

The lowest excited nπ* triplet of 9.10-anthraquinone, 1.4-naphthoquinone and 1,4-benzoquinone were studied in glassy matrices at 77 K using a time-resolved ESR method. The D value of the triplet state of 9,10-anthraquinone varied from ?0.351 cm^?1 in a polar solvent to ?0.318 cm^?1 in a non-polar solvent. Both 1,4-naphthoquinone and 1,4-benzoquinone in polar solvents showed triplet state spectra with a D value of ?0.330 cm^?1. A computer simulation revealed the existence of widely distributed zero-field splitting parameters in the glassy condition. These data are compared with an analysis of CIDEP results of para-quinones.     

Core-exciton spectra of AlxGa1−xAs studied with synchrotron radiation

Core-exciton spectra of Al_xGa_1?xAs have been measured in the photon-energy region from 19 to 27 eV by use of synchrotron radiation. The core-excitons associated with the Ga 3d core-hole and the conduction electron around the lowest L₆ and X₆ symmetry points are found to be coupled with each other through intervalley electron-hole interactions. Quantitative analyses have elucidated that intervalley Coulomb term is playing a dominant role for this coupling. Another higher energy doublet structure is interpreted as due to the transition from the Ga 3d core-levels to the rather flat region in the second lowest conduction band around the L₆ and L_{4, 5} symmetry points.     

Heating and quenching of metastable superconducting compounds with a plasma jet

Superconducting compounds, such as cubic -MoC_1–x, cubic -WC_1–x, hexagonal MoB₂, and cubic -TaN, which are metastable at room temperature, have been formed by heating and quenching of their respective equilibrium phases, such as hexagonal -MoC_1–x, hexagonal WC, rhombohedral Mo₂B₅, and hexagonal -TaN in a plasma jet. From calculations based on a simple model, the quenching rate of particles has been estimated to be 10⁵ deg s^–1.     

The primary fragmentation step of isoxazole upon electron impact. A correlation with photochemistry

Three isomeric compounds, I, II and III, were prepared and their mass spectra recorded. Comparisons of the spectra showed that the fragmentation of I proceeds only by way of II, and that II itself is transformed in part to III upon electron impact. It is suggested that selective ionization of each one of the two isolated functional groups in II may afford two isomeric radical ions, IIa and IIb. A possible interrelation to the photochemistry of these compounds is also discussed.     

A peptide motif recognizing a polymer stereoregularity

A combinatorial phage display method was applied to films composed of a stereoregular polymer of methacrylates. The phage clones with selective affinity for isotactic (it) poly(methyl methacrylate) (PMMA) were isolated. Greater amounts of the phage clones bound to it-PMMA, compared to other stereoregular PMMAs. The phage expressing ELWRPTR most strongly bound to the polymer, and the selectivity was also the best. The peptide motif essential for the specific interaction with the stereoregular polymer was revealed.