The intensities of the sequential twohyphen;photon ionization of Li2are evaluated starting fromabinitioCI electronic wave functions and using orthogonalized Coulomb functions for the continuum. The rotovibrational energies and the Franckndash;Condon factors are computed using a spline procedure both for the fitting of the electronic potentials and for the definition of the vibrational basis set. In agreement with experimental results, a substantial isotope separation is found for the three molecular isotopes of Li2and a wide spectrum of wavelengths useful for effective isotope enrichment is suggested. The modulation of the line intensities plays an important role in the fractionation process, while the energy matching criterion alone is not enough to establish which resonances are responsible for isotope enrichment. The importance of the Franckndash;Condon factor contributions to the spectrum modulation makes it possible to extend these results to other molecules.
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