Negative ion photoelectron spectroscopy of 2,2’-bithiophene cluster anions, (2T)n - (n = 1–100)

Cluster anions of 2,2’-bithiophene, (2T)_n^-, were produced up to n ∼500 in the gas-phase. The energetics of the excess electron in the (2T)_n^- clusters with n =1-100 were explored by negative ion photoelectron spectroscopy. When the vertical detachment energies (VDEs) obtained from the photoelectron spectra were analyzed by a plot against n^-1/3, it has been revealed that the excess electron trapping level thus extrapolated is located at ∼0.8 eV below the conduction band minimum (i.e. LUMO) of the 2T thin film. The large slope of the VDEs vs. n^-1/3 plot suggests that the neutral 2T molecules surrounding the anion core take non-planar twisted conformations with permanent dipole moments, resulting in the exceedingly deep trapping of the excess electron in the 2T cluster anions.     

Structural and valence changes of europium hydride induced by application of high-pressure H₂

Europium hydride EuH(x), when exposed to high-pressure H?, has been found to exhibit the following structural and valence changes: Pnma(x = 2, divalent) → P6?/mmc(x = 2, 7.2-8.7 GPa) → I4/m(x > 2, 8.7-9.7 GPa) → I4/mmm(x > 2, 9.7 GPa-,trivalent). With a trivalent character and a distorted cubic fcc structure, the I4/mmm structure is the β phase commonly observed for other rare-earth metal hydrides. Our study clearly demonstrates that EuH(x) is no longer an irregular member of the rare-earth metal hydrides.     

Studies on spintronics-related thin films using synchrotron-radiation-based Mössbauer spectroscopy

Applications of synchrotron-radiation-based Mössbauer spectroscopy in the “energy domain” to the studies on magnetism of thin films are introduced on the basis of the experiments recently performed at SPring-8, Japan. The measured samples are spintronics-related thin films, such as Co₂MnSn films, layered Fe/Cr films, layered Fe/Fe₃O₄ films, and Fe₄N films. The validity of the energy domain measurements is demonstrated in the light of industrial applications of magnetic thin films.     

On a question of Zariski on Zariski surfaces

We give a new method to construct unirational surfaces which may be applied to the following question posed by Zariski in his studies on unirational surfaces. Is any Zariski surface with geometric genus zero rational? Our main result is a negative answer to this question in any characteristic case.     

Nanoscale volcanoes: accretion of matter at ion-sculpted nanopores

We demonstrate the formation of nanoscale volcano-like structures induced by ion-beam irradiation of nanoscale pores in freestanding silicon nitride membranes. Accreted matter is delivered to the volcanoes from micrometer distances along the surface. Volcano formation accompanies nanopore shrinking and depends on geometrical factors and the presence of a conducting layer on the membrane's back surface. We argue that surface electric fields play an important role in accounting for the experimental observations.     

Butcher's simplifying assumption for symplectic integrators

Implicit Runge-Kutta methods with vanishingM matrix are discussed for preserving the symplectic structure of Hamiltonian systems. The number of the order conditions independent of the number of stages can be reduced considerably for the symplectic IRK method through the analysis utilizing the rooted tree and the corresponding elementary differentials. Butcher's simplifying condition further reduces the number of independent order conditions.     

Effect of hydrostatic pressure on the Neel temperature and the electrical residual resistivity of α-manganese

The electrical resistivity of α-Mn was measured from 4.2 K to 290 K at pressures up to 8 kbar. The residual resistivity was found not to depend on pressure. The Néel temperature decreases linearly with pressure at a slope dT_N/dP = − 1.7 ± 0.2 K/kbar.     

Site-specific phonon density of states discerned using electronic states

We have performed the measurement of the site-specific phonon densities of states (PDOS) discerned using electronic states. As far as we know, no general method could give the site-specific PDOS, although oscillating properties of the individual atoms in nonequivalent positions are not necessarily equivalent. However, the combination of the energy and time domain measurements of the nuclear resonant scattering of synchrotron radiation allows the identification of site-specific PDOS. We measured the site-specific PDOS of iron atoms in magnetite, which is a mixed valent compound, and the difference between partial phonon densities of the iron sites was clearly observed.