Absolute dipole oscillator strengths for molecular and dissociative photoionization of hydrogen fluoride

The internal rotation in the free anion radicals and the ion pairs from 3-nitroacetophenone and 4-nitroacetophenone is studied on the basis of their dynamic EPR spectra in solution. Energy barriers and related thermodynamic parameters which govern internal rotation and rotational diffusion of the studied systems have been provided together with a discussion about the accuracy and the reliability of their determination.     

Semi-empirical calculations and the assignment of valence photoelectron spectra of large molecules : Phenalen-9-amino-1-imine.

The He(I) photoelectron spectrum of phenalen-9-amino-1-imine (C₁₃H₁₀N₂) has been assigned using the SPINDO and HAM/3 semi-empirical methods. The molecular orbital patterns and properties suggested by the calculations are compared for the low energy region (7–12 ev).     

Cocycle Twisting of E(n)-Module Algebras and Applications to the Brauer Group

We classify the orbits of coquasi-triangular structures for the Hopf algebra E(n) under the action of lazy cocycles and the Hopf automorphism group. This is applied to detect subgroups of the Brauer group BQ(k,E(n)) of E(n) that are isomorphic. For any triangular structure R on E(n) we prove that the subgroup BM(k,E(n),R) of BQ(k,E(n)) arising from R is isomorphic to a direct product of BW(k), the Brauer-Wall group of the ground field k, and Sym_n(k), the group of n × n symmetric matrices under addition. For a general quasi-triangular structure R on E(n) we construct a split short exact sequence having BM(k,E(n),R⁾ as a middle term and as kernel a central extension of the group of symmetric matrices of order r < n (r depending on R). We finally describe how the image of the Hopf automorphism group inside BQ(k,E(n)) acts on Sym_n (k).     

Photoelectron spectroscopic studies of the monomers and dimers of acetic and trifluoracetic acids

Comparison of the He(I) and He(II) photoelectron spectra of acetic and trifluoracetic acids has clarified the assignments of their p-based ionization potentials. The He(I) spectra of the gas-phase homodimer of each molecule have been observed using a high-pressure nozzle inlet system operating at room temperature. Spectrum-stripping of the monomer—dimer mixed-spectra gives dimer spectra which are interpreted with the aid of molecular orbital calculations. Appropriate mixtures of the two acids have been analyzed to obtain the He(I) spectrum of the 1:1 heterodimer. Assignments of the three dimer spectra indicate that the inductive influences of the methyl and trifluoromethyl groups are transmitted across the hydrogen-bond bridges.     

The photoelectron spectra of N-bromo-methylamine and N,N-dibromo-methylamine

The UV photoelectron spectra of the reactive halamines, CH₃ NHBr (N-bromo-methylamine) and CH₃NBr₂ (N, N-dibromo-methylamine) have been obtained from measurements on the gas phase reaction products of CH₃NH₂ and Br₂. Spectrum-stripping was used to separate the two components from spectra obtained under different equilibrium conditions. The spectra correlate well with the results of molecular orbital calculations on the two molecules, and show that there is considerable pπ-pπ interaction in the NBr bond.     

Photoelectron spectroscopic assignment of the p-states of benzenethiol

He(I) anisotropy parameters and He(I)/He(II) relative band intensities have been determined and utilised to make a complete assignment of the benzenethiol p-electron-region photoelectron spectrum. The major S-atom contribution appears more so in the third band than in the first.     

Spherical conjugacy classes and involutions in the Weyl group

Let G be a simple algebraic group over an algebraically closed field of characteristic zero or positive odd, good characteristic. Let B be a Borel subgroup of G. We show that the spherical conjugacy classes of G intersect only the double cosets of B in G corresponding to involutions in the Weyl group of G. This result is used in order to prove that for a spherical conjugacy class with dense B-orbit v ₀ ⊂ BwB there holds extending to the case of groups over fields of odd, good characteristic a characterization of spherical conjugacy classes obtained by Cantarini, Costantini and the author. It is also shown that the weights occurring in the G-module decomposition of the ring of regular functions on are self-adjoint and they lie in the −1-eigenspace of the element w.     

Determination of folate vitamers in food and in Italian reference diet by high-performance liquid chromatography.

A trienzyme treatment (conjugase, alpha-amylase, protease) followed by affinity chromatography and reversed-phase HPLC with UV and fluorescence detection was performed for the quantification of folate vitamers in legumes (chickpea and beans), processed meats (salami Milano and Parma ham) and in an Italian reference diet. This method allowed a good separation of six folate vitamers: 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, folic acid, 10-formylfolic acid, 10-formyldihydrofolate and tetrahydrofolate within 30 min. Recovery, reproducibility and limits of detection of the method are reported. HPLC results were 24-52% lower than the microbiological assay findings.     

On the q -Convolution on the Line

The investigation of a q -analogue of the convolution on the line, started in conjunction with Koornwinder, is continued, with special attention to the approximation of functions by means of the convolution. A new space of functions that forms an increasing chain of algebras (with respect to the q -convolution), depending on a parameter s>0 , is constructed. For a special value of the parameter the corresponding algebra is commutative and unital, and is shown to be the quotient of an algebra studied in a previous paper modulo the kernel of a q -analogue of the Fourier transform. This result has an analytic interpretation in terms of analytic functions, whose q -moments have a (fast) decreasing behavior and allows the extension of Koornwinder's inversion formula for the q -Fourier transform. A few results on the invertibility of functions with respect to the q -convolution are also obtained and they are applied to the solution of certain simple linear q -difference equations with polynomial coefficients.     

Absolute dipole oscillator strengths for photoabsorption and photoionization of carbon disulphide

The absolute dipole oscillator strengths (cross-sections) for photoabsorption and photoionization (total and partial) of CS₂ have been obtained in the 5–40 eV energy range by magic-angle dipole (e, 2e) spectroscopy. Very strong absorption is detected below 20 eV, much of which is attributable to the excitation of molecules decaying by autoionization processes. Analysis of binding energy spectra taken at energy losses above 20 eV reveals extensive satellite structure in the range up to 35 eV. This structure is attributed to many-electron effects consistent with theoretical calculations found in the literature. Photoelectron branching ratios for CS₂ are also reported.