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sufficient amount of experimental data is available because this solution is obtained
as a result of optimization of a large number of experiments in different spectrum
regions; and (4) the reverse problem is reduced to analysis of the sets of simple
algebraic equations.
In conclusion, we discuss the effects associated with a field mixing of the Rydberg
resonances. The presence of an external field leads to the fact that the resonance
structure of the intermediate Rydberg complexes XY** may overlap some of the
resonances belonging to the different vibronic series of the quasi-energy spectrum,
which can occur at any ratio between the vibrational ! and field ! f frequencies.
If the field widths are smaller compared with the natural ones, the Rydberg states
experience almost no exposure to laser radiation. The situation changes significantly
if a resonance level of a predissociative Rydberg series overlaps with the field-
induced resonant level. The composite resonant vibronic (hybrid) states will arise
in these conditions. The mechanisms of population and decay of these states during
the DR reaction must differ significantly from those discussed here. In this case,
new channels of the process will arise, when the effective lƒ-harmonics take place,
which occurs as the result of a weak configuration interaction with the dissociative
channels being in the field excluded from the process. Because the existence
conditions of the field-induced resonances of composite e C XY C systems are very
critical to the positions of the unperturbed resonance levels, the rotational structure
of the intermediate Rydberg complexes should be included in consideration.
Let us demonstrate the main features of the resonance state field mixing on
an example of the DR reaction in the most important case, when the incident
electron energy E in a given .lƒ; v D 0;m D 0/ state is located below the ion
vibrational excitation threshold. We consider the situation when the “natural”
vibronic resonance of 1 .lƒ; v D 1;m D 0/ with the energy E 1 overlaps with the
laser-induced resonance of 2 .l 0 ƒ 0 ; v D 1;m 1/, whose energy is equal to E 2 ,
and denote the continuum e C XY C .m D 0/ and X C Y.m 1/ states by
0andˇ, respectively. Then, the DR reaction, taken in the field absence .f D 0/
of the direct and resonant mechanisms and described by the Fano outline, obtains
additional features in energy dependence under a field mixing with the laser-induced
resonance 2. Indeed, neglecting the field-induced shift and broadening of the levels,
the transition probability can be written as (Golubkov and Ivanov 1993 )
ˇ ˇ ˇ ˇ ˇ
ˇ ˇ ˇ ˇ ˇ
." 1 1 / " 2 C i 2 V 12 2
" 1 C i 1 " 2 C i 2 / .V 12 2
W ˇ0 D W 0
Here W 0 is the probability of direct transition in the absent external field, " 1.2/ D
E E 1.2/ are the values measured from the resonant level energies, 1.2/ are the
natural half-widths of these levels expressed in terms of partial ionization rate
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