A Mild Method for the Formation of Tosylhydrazone Derivatives from Keto Esters

An improved preparation of tosylhydrazones of α- and β-keto esters, by means of active aluminium oxide as catalyst, are described.     

Observation of a compressed state of the quantum wire material in porous silicon by the method of Raman scattering

An experiment on Raman scattering in porous silicon containing a regular system of quantum wires reveals a shift of the phonon frequencies of the silicon lattice toward higher energies. The effect is interpreted as a manifestation of a compressed state of the material in the quantum wires. It is shown that the observed deformation plays a large role in the formation of the structure of porous silicon. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 695–700 (25 November 1996)     

Disproportionation, metal-insulator transition, and critical interaction strength in Na(1/2)CoO2

Charge disproportionation (CD) and spin differentiation in Na(1/2)CoO2 are studied using the correlated band local-density approximation + Hubbard U (LDA+U) approach. The simultaneous CD and gap opening seen previously is followed in detail through a first-order charge disproportionation transition 2Co(3.5+)-->Co3++Co4+. Disproportionation in the Co a(g) orbital results in half of the ions (Co3+) becoming electronically and magnetically dead, transforming the quarter-filled a(g) system into a half-filled subsystem that subsequently undergoes the observed charge ordering or metal-insulator transition. Comparing with data in the x approximately 0.3 regime suggests the system has moved into the multiband regime where the effective Coulomb repulsion U-->U(eff)=U/sqrt[3] strongly lessens correlation effects.     

N-H..S hydrogen bonds

Infrared spectra of some compounds containing weak and medium-strong NH..S hydrogen bonds have been investigated. Spectroscopic and structural data have been correlated and compared with those obtained for NH..O and NH..N systems. At the same strength, the N..S distance is 0.51 and 0.36 Å longer than the corresponding N..O and N..N distances, respectively.     

MO-Berechnungen an Heterocyclen, 24. Mitt.: Eine Interpretation der UPS der 2,2′-und 4,4′-Bipyridyle und deren N-Monoxide

The He I photoelectron spectra (UPS) of the 2,2- and 4,4-bipyridyls and their mono-N-oxides habe been reported and interpreted on the basis of modified CNDO-type calculations. The calculations show that the sequence of the eigenvalues _i is nearly independent from the dihedral angle around the central bond and that the different pattern of the _i must be related to the different positions of the N-atoms. For the N-oxides an assignment is given up to 12eV using the calculated results. Furthermore, the conformations of these compounds has been discussed.

23. Mitt.:Remane, H., Kluge, G., Scholz, M., Z. phys. Chem. (Leipzig), im Druck.     

Neutron inelastic scattering spectra of strongly hydrogen bonded acid oxalates NaHC2O4, KHC2O4 and LiHC2O4

Neutron inelastic scattering spectra of NaHC₂O₄, KHC₂O₄ crystals at 80 K have been recorded in the 2200-200 cm^?1 range. The lithium acid salt was also studied at different temperatures. NIS spectra are compared to the corresponding infrared and Raman spectra and an assignment is proposed. Two strong bands near 1500 and 1100 cm^?1 are assigned to δ(OH) and γ(OH) vibrations, respectively, while five weak bands below 900 cm^?1 are associated with skeletal modes, mainly bending vibrations. The OH stretching vibration is not observed and is believed to be hidden by other bands; the peak intensity must be low because of its band width which is of the order of a few hundreds wavenumbers.     

KL0-KS0 transmission regeneration on hydrogen

The energy dependence of the modulus and phase of the K_L⁰-K_S⁰ regeneration amplitude on hydrogen in the range of 14–50 GeV has been investigated at the Serpukhov 70 GeV accelerator.It has been established that the modulus of the modified regeneration amplitude decreases with increasing momentum as $\text{2|?}{}_{21}{}^0\text{(p)|/k = (0.84 ± 0.42) · p}{}^{\mathrm{?0.50\pm 0.15}}\text{mb}$. The amplitude phase is energy-independent and its mean value is ?₂₁⁰ = ?132° ± 5°. The results obtained are compared with other experiments and with predictions of different theoretical models.