The rates of the electric quadrupole E2 and magnetic dipole M1 forbidden transitions in the ground configuration and some excited configurations of the Ti XIX ion have been calculated. The multiconfiguration Hartree Fock (MCHF) method has been used. The relativistic corrections are included in the Breit Pauli approximation. A detailed comparison of the present theoretical results with previous ...

A comprehensive investigation of the pp*, np* and ps* excited states of xanthine has been performed with the CASSCF, CASPT2, CC2 and ADC(2) methods. The 7H-diketo and 9H-diketo tautomers of xanthine, which are the lowest-energy tautomers in the ground state, have been studied. Out-of-plane deformation of the purine system in the lowest pp* state as well as dissociation of the NH bonds in the lo...

Low-energy electron impact excitations of S2 molecules are studied using the fixedbond R-matrix method based on state-averaged complete active space SCF orbitals. Integral cross sections are calculated for elastic electron collision as well as impact excitation of the 7 lowest excited electronic states. Also, differential cross sections are obtained for elastic collision and excitation of the a...

Different types of Gaussian basis sets for accurate LCAO calculations are discussed. For calculations designed to recover a substantial portion of the correlation energy, we suggest the use of basis sets comprising natural orbitals from correlated calculations on the atoms. These basis sets have proven to be very efficient in accounting for large fractions of the molecular correlation energy. F...