Development of dual-beamline photoelectron momentum microscopy for valence orbital analysis.

The soft X-ray photoelectron momentum microscopy (PMM) experimental station at the UVSOR Synchrotron Facility has been recently upgraded by additionally guiding vacuum ultraviolet (VUV) light in a normal-incidence configuration. PMM offers a very powerful tool for comprehensive electronic structure analyses in real and momentum spaces. In this work, a VUV beam with variable polarization in the normal-incidence geometry was obtained at the same sample position as the soft X-ray beam from BL6U by branching the VUV beamline BL7U. The valence electronic structure of the Au(111) surface was measured using horizontal and vertical linearly polarized (s-polarized) light excitations from BL7U in addition to horizontal linearly polarized (p-polarized) light excitations from BL6U. Such highly symmetric photoemission geometry with normal incidence offers direct access to atomic orbital information via photon polarization-dependent transition-matrix-element analysis.

Acceptance-cone-tunable electron spectrometer for highly-efficient constant energy mapping.

We have developed an acceptance-cone-tunable (ACT) electron spectrometer for the highly efficient constant-energy photoelectron mapping of functional materials. The ACT spectrometer consists of the hemispherical deflection analyzer with the mesh-type electrostatic lens near the sample. The photoelectron trajectory can be converged by applying a negative bias to the sample and grounding the mesh lens and the analyzer entrance. The performance of the present ACT spectrometer with neither rotating nor tilting of the sample is demonstrated by the wide-angle observation of the well-known π-band dispersion of a single crystalline graphite over the Brillouin zone. The acceptance cone of the spectrometer is expanded by a factor of 3.30 when the negative bias voltage is 10 times as high as the kinetic energy of photoelectrons.

Synthesis and characterization of a DNA analogue stabilized by mercapto C-nucleoside induced disulfide bonding.

A redox-active nucleobase analogue of a nucleotide was synthesized and incorporated into DNA using phosphoramidite chemistry. An analogue-containing oligonucleotide in the absence of a reducing reagent formed a stable duplex with a substantially higher melting temperature compared to that of a standard DNA duplex of the same length.