Rydberg states of HCN observed by electron impact spectroscopy

The electron energy loss spectrum of HCN has been determined in the energy region 8–13.6 eV at impact energies of 100, 50 and 30 eV. It is shown that energy loss spectra of HCN at intermediate impact energies can be satisfactorily analysed unlike the diffuse unassigned optical absorption spectra that have previously been reported. Rydberg series have been assigned using term values and quantum defects together with ionization potentials obtained by photoelectron spectroscopy.     

On the lewis acid catalyzed diels-alder reaction of furan. regio- and stereospecific synthesis of substituted cyclohexenols and cyclohexadienols.

The [4+2] cycloaddition between furan and some dienophiles can be greatly accelerated in the presence of a Lewis-Acid (i.e. ZnI₂. The 7-oxabicyclo [2.2.1] heptyl system readily undergoes a base promoted β-elimination of the heteroatom bridge leading to substituted cyclohexenols and cyclohexadienols.     

Electronic spectra of aliphatic carbonyl compounds by electron impact spectroscopy: II. Saturated ketones

Electron impact energy loss spectra of acetone, 2-butanone, methyl isobutyl ketone, methyl isopropyl ketone, and methyl tertiarybutyl ketone have been recorded at an impact energy of 100 eV and a scattering angle of two degrees. Rydberg assignments have been made using quantum defects and term values obtained by reference to ionization potentials measured by photoelectron spectroscopy. Substituent effects on Rydberg orbital energies are discussed using Taft σ* values.     

The assignment of the ionization potentials of formaldehyde by an (e, 2e) experiment

The angular variation of the binding energy spectrum in an electron-electron coincidence experiment indicates that the third and fourth ionization potentials of formaldehyde are due to the 5a₁ and 1b₂ orbitals respectively. The vertical ionization potentials of the 4a₁ and 5a₁ orbitals are found to be 21.15 ± 0.15 and 34.2 ± 0.2 eV respectively.     

The valence orbitals of NH3 by electron momentum spectroscopy: Quantitative comparisons using Hartree-Fock limit and correlated wavefunctions

The complete valence shell binding energy spectra and valence orbital electron momentum distributions for NH₃ have been measured by high-momentum-resolution electron momentum spectroscopy (EMS). The results are quantitatively compared with theoretical calculations using SCF wavefunctions ranging from DZ quality to a newly developed 126-GTO wavefunction essentially at the Hartree-Fock limit. The 3a₁ and to a lesser extent the 2a₁ valence orbital are not adequately described even at the Hartree-Fock limit with basis set saturation including diffuse functions. The differences between theory and experiment are largely resolved by ion-neutral overlap calculations using CI wavefunctions to incorporate the effects of electron correlation. The 126-G (CI) wavefunctions provide accurate calculation of a wide range of electronic properties of NH₃ and also give good quantitative prediction of the three valence orbital momentum distributions as well as a reasonable prediction of the many-body pole strength distribution observed in the (2a₁)⁻¹ inner valence binding energy spectrum. The present EMS results are compared with recent investigations of wavefunction tails by exterior electron distribution calculations and Penning ionization electron spectroscopy measurements reported by Ohno et al.     

Evidence for lipids-calcium ions interactions using fluorescent probing in paediatric nutrition admixtures

The aim of this work was to envisage a new analytical fluorescent method to study the molecular interactions between cations and negatively charged lipid droplets contained in total parenteral nutrition (TPN) admixtures. For this purpose, two fluorescent probes were tested: 9-diethylamino-5H-benzo[alpha]phenoxazine-5-one, commonly named nile red (NR), and 2-(p-toluidinyl)-naphthalene-6-sulfonate (TNS). NR, a neutral molecule, and TNS, an anionic one, are both polarity probes. Their fluorescence emission was enhanced in an apolar environment. They were used at 1 and 2.5 muM, respectively. Results showed that scattered light was very intense in weak aqueous dilution (1/10 vv(-1)) of fat emulsion and appeared as an experimental constraint. The sensitivity of fluorescence measurement in fat emulsion samples was constantly higher for NR than for TNS. When calcium addition occurs, as in pharmaceutical practice, a dramatic increase of fluorescence emission signal was showed for TNS, but no effect was observed for NR. As a conclusion, it was pointed out that the interactions between lipid droplets and calcium ions were likely to take place at the interface of the droplet and that TNS was a more appropriate probe than NR to prove it. Thus, fluorescent probing appeared to be a convenient new analytical tool for the investigation of lipid-cations interactions in TPN mixtures.     

Mass spectral studies of stereoisomers: The photoionisation of some substituted cyclohexanols

The fragmentation of the stereoisomers of 4-t-butylcyclohexanol, and 3-methylcyclohexanol has been studied by photoionisation mass spectrometry at 1216 Å and 584 Å. Deuterium substitution and high resolution mass spectrometry have been used to gain further insight into the fragmentation pathways.     

The Huggins band of ozone: assignment of hot bands

The "hot bands" of the Huggins band of ozone are assigned, in both the 218 K and the 295 K spectrum. The assignment is based on intensities calculated with three-dimensional vibrational wave functions for the electronic ground state (X) and the excited state (B). The hot-band structures in the 218 K spectrum all can be assigned to transitions starting from vibrational states with one quantum of stretching excitation in the ground electronic state. The 295 K spectrum shows new structures, which are due to transitions originating from vibrational states in the X state with two quanta of excitation of the stretching modes--despite very small Boltzmann factors. All structures in the low-energy range of the 295 K spectrum, even the very weak ones, thus can be uniquely interpreted. The significance of hot bands results from the strong increase of Franck-Condon factors with excitation of the stretching modes in both the lower and/or the upper electronic states, whose equilibrium bond lengths differ significantly.     

Magnetic structure of the spin-1/2 layer compound NaNiO2

We have carried out high resolution neutron powder diffraction experiments aiming at a determination of the magnetic structure of the S=1/2 layer compound NaNiO2. The magnetic moments are ferromagnetically aligned in the NiO2 layers and antiparallel between layers. The direction of the magnetic moment has a small component along the a-direction.