Excited states of highly stripped ions

Time dependent perturbation theory (TDPT) has been very successful in predi cting the positions of the excited energy levels of atomic and molecular sy stems. TDPT can be associated with different formalisms to yield results of different degrees of accuracy. The method was originally used to predict s tructure properties connected with single excitations. However, later devel opments show its potentiality towards evaluation of atomic data connected w ith double and multiple excitations. In the present context we have used TD PT within a variational framework to calculate singly and doubly excited en ergy levels of several highly stripped ions of different electronic configu rations and estimated their transition properties like oscillator strengths , transition probabilities, etc. A free atom or ion is subjected to a time- dependent external harmonic field and the linear response properties of the atom are evaluated. The effect of the external field is to generate single or multiple excitation of the electronic charge cloud. Depending upon the nature of the perturbing field one can get allowed as well as forbidden tra nsitions involving spatial and spin symmetries. The positions of the excite d energy levels and analytical representations of their wave functions are directly obtained from our formalism by analysing the positions of the pole s of an appropriately constructed linearised variational functional with re spect to external frequency. Transition energies and other structural param eters agree well with existing data wherever available.