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Fig. 1.2 Potential curves for the molecular ion XY C and the quasi-molecular XY * . The excitation
energy of the atom Y *
is smaller than the ionization potential of the atom X
preconditions do not violate, can be estimated from the ratio of the de Broglie
wavelength of the atom and the characteristic atomic size, a 0 . All this has led to the
development of Penning electron spectroscopy as a new direction of experimental
If the excitation energy X * is smaller than the Y ionization potential, than there
are two possibilities: reaction (1.8) and (1.9) (in the diabatic representation). The
first case takes place when the potential curves of the quasi-molecule U ˇ and the
molecular ion U i do not overlap (Fig. 1.2 ). In this case, the transition occurs because
of the nonadiabatic coupling of the electron and nuclear motions in a wide range of
interatomic distances R , when they approach, and the potential curves of Rydberg
states of the quasi-molecule X ** Y are the Coulomb condensation. The second case
corresponds to the situation when, in the vicinity of the point R c , the potential
curve XY * , and the dissociative term (diabatic picture) intersects a set of curves
of the Rydberg and ion U i terms (Fig. 1.3 ). When going to the region of interatomic
distances R < R c ,thetermXY * becomes autoionization. Consequently, the reaction
of the AI here is essentially a multichannel process, as occurs with the participation
continuums of the Rydberg, dissociative, and ionized states (see Figs. 1.2 , 1.3 ). As
a result of the direct relationship of the Rydberg XY ** , the dissociative X *
C Y,
the intermediate valence X * Y, and the ionic X C Y configurations, under the atom
collisions are possible not only autoionization, but inelastic transitions, that can be
accompanied with the increase (or decrease) of the initial atom excitation energies.
Analysis of the discrete level interaction with the states of the continuum and
the infinite sequence of the Coulomb levels was carried out (Demkov and Komarov
1966 ). Strictly speaking, the problem of multiple transitions (associated with the
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