A computational model and corresponding computer program for calculating the 2S+1LJ energy levels, reduced matrix elements, Stark energy levels of crystal field, state-state transition oscillator strength between crystal energy levels, and for modulating the absorption spectrum of f-element were developed based on irreducible tensor operator method. The energy levels of free metallic ion were calculated with a 13 parameters model including the 2-body and 3-body interactions. The Stark energy levels of crystal field were calculated using the model proposed by Newman based on 1 electron orbital approximation The f-f oscillator strength calculation includes the contribution of electrostatic-induced, ligand polarization, vibronic-induced, magnetic dipolar transitions.

Key words: COMPUTER APPLICATIONS, COMPUTERIZED SIMULATION, LANTHANON, SPECTROGRAPHIC ANALYSIS, TRANSITION, IRREDUABLE REPRESENTATION