For the evaluation of the time consumption of the two approaches, a damped calculation was carried out with a real frequency of 0.20 a.u. and a damping factor of 4.5563•10 -3 a.u. . The frequency 0.20 a.u. lies in the upper L-band region, right "at the border" with the spectrally dense region. The resonant calculations were carried out for the lowest-energy degenerate set consisting of the first transitions of B 2u and B 3u symmetry.