Influence of resonant states mixing of three-level system on the realization of multiphoton transitions

Summary form only given. The experimental investigations of effect of resonant mixing of states of three-level system and multiphoton transitions from them under the influence of one and two laser fields were performed. The Ba atoms were investigated. Resonant mixing of ground (6s ^{2 1}S₀), first resonant (6s6p ¹P₁⁰) and metastable (6s5d ³D₂) states was studied. The radiation of two tunable lasers: dye laser (DL) and laser on color centres (LCC) was used. The frequency of DL was fixed at (ω2 = 18060 cm^-1 corresponding to one-photon transition 6s^{2 1}S₀ → 6s6p ¹P₁⁰. The frequency of radiation of LCC ((Di) was varied in vicinity of frequency ωmn = 8845 cm^-1 relevant to one-photon transition 6s5d ³D₂ → 6s6p ¹P1. The field strengths of DL and LCC were equal to ε=6×10⁴ V/cm and ε = 2×10⁶ V/cm, correspondingly. The polarization of both radiations was linear with parallel orientation of light vectors. Under the influence of two laser radiation on Ba atoms the resonant mixing of the states of three-level systems occurs. Resulting this the populations of these three states depend on the value of matrix elements of mentioned one-photon transitions. The estimations show that the population of mentioned above three states must be of the same order of magnitude. Under the simultaneous act ion of two laser fields on the beam of Ba atoms except population of all three states the one and multiphoton transitions from these states can be realized. The investigation of such transitions was performed by the method of measurement of the Ba ions yield, formed in result of ionization of Ba atoms in two laser fields. The result of these measurements shows that in the Ba⁺ yield side by side with transitions allowed by selection rules for dipole approach the forbidden transitions are. manifested. It must be noted that the amplitudes of maxima caused by forbidden transition are the same as the amplitudes of maxima caused by allowed transitions.