Lorentz Invariance and the retarded Bohm Model

We show how a recently introduced retarded version of the Bohm Model evades the Hardy proof that hidden-variable models must violate Lorentz Invariance. We also discuss a possible test of such models.We are happy to have this article included in a volume honoring Jean-Pierre Vigier, who has long recognized the significance of the hidden-variable model following from the work of L. de Broglie and D. Bohm.S.W.M. would like to thank S.E.R.C. for financial support.     

Effects of alkylation upon the proton affinities of nitrogen and oxygen bases

The protonation energies of alkylated derivatives of NH₃ and OH₂ are calculated at the Hartree–Fock level with the split-valence 4-31G basis set. The methyl, dimethyl, and ethyl amines are studied; oxygen bases include methanol, dimethylether, and ethanol. The geometries of each molecule and its protonated analog are fully optimized. It is found that protonation leads to significant changes in the molecular structures. In particular, the bonds to the N and O atoms are substantially elongated, especially when the other atom involved is C rather than H. The calculated absolute proton affinities are somewhat larger than the experimental values. However, the differences in protonation energies of the various molecules relative to one another agree quantitatively with experiment. Replacement of one H atom of the base by a methyl group induces an increase in proton affinity of some 10 kcal/mol. If a second methyl group is added to the N or O atom, a further increment of about 70% this amount is noted. On the other hand, placement of the second C atom on the first methyl group (to form an ethyl substituent) leads to a smaller increase (～30%). The magnitudes of these alkyl substituent effects are somewhat larger for the oxygen bases than for the amines.     

Structural and Dynamic Study of SnCl4 · 2 Me2O and SnCl4 · 2 Me2Se Preliminary communication

The solid cis-SnCl₄ · 2Me₂O and trans-SnCl₄ · 2Me₂Se adducts have been synthesised and characterised by IR. and Raman spectroscopy. NMR. and vibrational spectroscopy show a fast cis-trans equilibrium for both complexes in solution in an inert solvent.     

Direct imaging of surface-enhanced Raman scattering in the near field

By using near-field scanning microscopy/spectroscopy, we show that surface-enhanced Raman scattering (SERS) of rhodamine 6G deposited on self-affine silver colloidal film is localized to small, down to less than 200 nm, portions of the film. The locus of the SERS signals ("hot spots") does not necessarily reside in special topographic elements such as interstices and between nanoparticles. The local SERS enhancement is estimated to be over 3 orders of magnitude higher compared to the far-field measurements. Near-field imaging of SERS directly validates the theory of the optical response of self-affine fractal objects.     

Low-temperature activation and deactivation of high-Curie-temperature ferromagnetism in a new diluted magnetic semiconductor: Ni2+-Doped SnO2

We report the synthesis of colloidal Ni(2+)-doped SnO(2) (Ni(2+):SnO(2)) nanocrystals and their characterization by electronic absorption, magnetic circular dichroism, X-ray absorption, magnetic susceptibility, scanning electron microscopy, and X-ray diffraction measurements. The Ni(2+) dopants are found to occupy pseudooctahedral Sn(4+) cation sites of rutile SnO(2) without local charge compensation. The paramagnetic nanocrystals exhibit robust high-Curie-temperature (T(C)) ferromagnetism (M(s)(300 K) = 0.8 mu(B)/Ni(2+), T(C) > 300 K) when spin-coated into films, attributed to the formation of interfacial fusion defects. Facile reversibility of the paramagnetic-ferromagnetic phase transition is also observed. This magnetic phase transition is studied as a function of temperature, time, and atmospheric composition, from which the barrier to ferromagnetic activation (E(a)) is estimated to be 1200 cm(-1). This energy is associated with ligand mobility on the surfaces of the Ni(2+):SnO(2) nanocrystals. The phase transition is reversed under air but not under N(2), from which the microscopic identity of the activating defect is proposed to be interfacial oxygen vacancies.     

A vibrational sum frequency spectroscopy study of the liquid-gas interface of acetic acid-water mixtures: 1. Surface speciation

Aqueous acetic acid solutions have been studied by vibrational sum frequency spectroscopy (VSFS) in order to acquire molecular information about the liquid-gas interface. The concentration range 0-100% acetic acid has been studied in the CH/OH and the C-O/C=O regions, and in order to clarify peak assignments, experiments with deuterated acetic acid and water have also been performed. Throughout the whole concentration range, the acetic acid is proven to be protonated. It is explicitly shown that the structure of a water surface becomes disrupted even at small additions of acetic acid. Furthermore, the spectral evolution upon increasing the concentration of acetic acid is explained in terms of the different complexes of acetic acid molecules, such as the hydrated monomer, linear dimer, and cyclic dimer. In the C=O region, the hydrated monomer is concluded to give rise to the sum frequency (SF) signal, and in the CH region, the cyclic dimer contributes to the signal as well. The combination of results from the CH/OH and the C-O/C=O regions allows a thorough characterization of the behavior of the acetic acid molecules at the interface to be obtained.     

Improvement of polarized double-zeta basis sets for molecular interactions. Complexes of NH3, OH2, and FH with H+ and Li+

Interaction energies of a proton and lithium cation with NH₃, OH₂, and HF axe computed at the SCF and Møller-Plesset levels. It is found that the basis set superposition errors at all levels with the 6-3 1G** basis set may be greatly reduced by including an additional diffuse sp shell on first-row atoms; the exponent of this shell has been optimized to 0.1.     

Synthesis of side chain truncated 3"-aldehyde, 3"-carboxylic acid, and 1"-aldehyde from nodulisporic acid A

An efficient synthesis of the truncated 3"-aldehyde (3) from nodulisporic acid A (1) under mild conditions is described. Further oxidation of 3 to 3"-carboxylic acid (4) and its subsequent oxidative degradation produced 1"-aldehyde (5). These new derivatives are versatile intermediates for the preparation of new, side chain modified derivatives of nodulisporic acid A. [reaction: see text]