Analytical Study of Extracts of St John’s Wort (Hypericum perforatum), Evaluation of HPTLC Plates by Multivariate Data Analysis

JPC – Journal of Planar Chromatography – Modern TLC - HPTLC with multivariate data analysis has been used as a new means of evaluating the quality of herbal extracts. Spectral data from...     

Theory and computational methods for studies of nonlinear phenomena in laser spectroscopy. I. General formalism

A general formalism will be outlined, which uses steady-state wave functions for the study of nonlinear phenomena occurring in molecular systems interacting with intense electromagnetic fields. The steady-state approach has the advantage of being free from the secular divergencies and normalization terms which appear in a perturbation expansion of the time-dependent wave function. A physical interpretation of the steady states will be given by considering the interaction between the molecule and the quantized electromagnetic field. The steady states appear as states of the combined system molecule plus electromagnetic field, with eigenvalues corresponding to the energy levels of the combined system in a semiclassical approximation. Evolution operators will be introduced and used to derive formulas for n-photon transition probabilities between molecular states both in the ordinary configuration Hilbert space and in the composite Hilbert space spanned by the steadystate wave functions.     

On the ordering of the ionization energies in N2: A MC SCF study of near-degeneracy effects

Single configuration SCF wavefunctions yield poor results for the order and relative energies of low-lying icnic states of N₂. A multi-configurational SCF (MC SCF) model which takes account of the near degeneracy of a small number of strongly and weakly occupied orbitals corrects the errors of the SCF approach. MC SCF results for N₂ predict the correct ordering and give reasonably accurate results for the three lowest ionization potentials.     

Quantum chemistry predicts multiply bonded diuranium compounds to be stable

Results from quantum chemical calculations that predict the existence of a series of diuranium molecules are reported. Two diuranium chlorides, U(2)Cl(6) and U(2)Cl(8)(2)(-), and three different carboxylates, U(2)(OCHO)(4), U(2)(OCHO)(6), and U(2)(OCHO)(4)Cl(2) have been studied. All species have been found to be stable with a multiply bonded U(2) unit.     

Weighted Bergman kernels and virtual Bergman kernels

We introduce the notion of virtual Bergman kernel and study some of its applications.     

Ground-state dipole polarizability of lithium hydride. Accurate SCF and CAS SCF calculations

Accurate calculations of the dipole polarizability tensor of lithium hydride are performed using the finite-field perturbation approach in the SCF and CAS SCF method. The SCF results (α_? = 22.1, α_⊥ = 25.4 au) are expected to be very close to the HF values. The CAS SCF calculations predict a positive correlation contribution, giving α_? = 26.3 and α_⊥ = 29.3 au.