Spectrum of the barium atom in a laser radiation field

Peculiarity of formation of doubly charged ions upon multiphoton ionization of barium atoms by linearly and circularly polarized radiation

“…As we see, the yield of Ba + ions shows the manifestation of the two-photon excitation of the bound one-and two-electron states, which are singlet or triplet. Note that, previously, the excitation of the same states was also observed at low field strengths, ε=4×10 4 V/cm [16]. It is noteworthy that most of these states (the states with total momentum J=2) can be excited by circularly polarized radiation as well.…”

“…It is well known that the probability of resonance multiphoton ionization of atoms considerably exceeds the probability of nonresonance ionization. Our investigations [16] show that the probability of the resonance formation of Ba + ions is approximately 10 4 times higher than the probability of the nonresonance formation of these ions. Hence, the saturation of the resonance three-photon ionization of Ba atoms should be reached in a considerably shorter time than the saturation of the nonresonance process.…”

“…The resonance maxima observed in the dependences N + (ω) at low field strengths ε were thoroughly discussed and identified in our previous publication [16]. The resonance maxima observed in the dependences N + (ω) at high field strengths ε are associated with two-photon excitation of the following bound states of the Ba atom: 5d7s 1 D 2 (ω t =16 897 cm -1 ), 6p 2 1 S 0 (ω t =17 183 cm -1 ), 6p2 3 P 0 (ω t =17 246 cm -1 ), 6p 2 1 D 2 (ω t =17 672 cm -1 ), 6p 2 3 P 2 (ω t =17 808 cm -1 ) and 6s7d 3 D 2 (ω t =17 881 cm -1 ).…”

Three-Photon Ionization with One-Photon Resonance between Excited Levels

“…One-and two-photon resonantly enhanced three-photon ionization has been extensively studied via experiment, and to a lesser extent theoretically (see for example Refs. [7][8][9][10][11][12]).…”

“…Experimental manifestation of transitions such as (3) has been observed at threephoton ionization of a number of atoms, in particular Na, Rb, Ba, and Yb (see for example Refs. [11,[13][14][15]). Thus, at three-photon ionization of the Ba atom [11] in the vicinity of the maxima related to the one-photon 6s 2 1 S 0 → 6s6p 1 P o 1 (ω = 18,060 cm −1 ) and twophoton 6s 2 1 S 0 →5d6d 3 D 2 (ω = 18,100 cm −1 ) transitions from the ground 6s 2 1 S 0 level (transitions 1→2 and 1→3, respectively), a clear maximum corresponding to the one-photon 6s6p 1 P o 1 → 5d6d 3 D 2 (ω = 18,140 cm −1 ) transition between the excited levels (transition 2→3) was also observed.…”