1 EXTRA SUB-DOPPLER LINES IN THE VICINITY OF THE THIRD RESONANCE 6S-8P OF ATOMIC Cs ATTRIBUTED TO OPTICALLY INDUCED Cs DIMERS

33.20.Xx Spectra induced by strong-field or attosecond laser irradiation 32.80.Wr Other multiphoton processes 33.20.Kf Visible spectra (molecules) 82.20.Rp State to state energy transfer We report on the observation of extra sub-Doppler lines in a saturated absorption experiment when exploring the vicinity of the 6S1/2-8P3/2 transition of Cs ( = 388 nm). These extra lines are observed only under a relatively strong irradiation of both the pump and the probe beams. Extra narrow lines are also observed in co-propagating nonlinear spectroscopy, and around the lines of the V-type three-level system 8P3/2- 6S1/2- 8P1/2 (1 = 388 nm, 2 = 389 nm). We attribute theses extra-lines to a probing of high-lying molecular caesium, produced as a result of the optical excitation of Cs atoms, as the low Cs atom density ( 1012cm-3) is unable to populate significantly the dimer states in the condition of thermal equilibrium. ha l-