Example: dissociative attachment and vibrational excitation

Dissociative attachment (1) and vibrational excitation (2) are the processes of electron-molecule interaction.

AB + e- → AB- → A + B-     (1)

AB(v) + e- → AB- → AB(v’) + e-    (2)

These two processes compete one with another and play an important role in plasma discharges (for example, in plasma lamps),  gas dielectrics, plasma lasers, optogalvanic phenomena, modes in plasma e. t. c.

One of the most visual and obvious method of investigation of dissociative attachment and vibrational excitation is semiclassical analysis. At the heart of this method is the formula of Breit and Wigner for resonant scattering and underlying suggestion about classical nature of nuclei motion.

Dissociative attachment to HCl

HCl is an electronegative molecule, so process of dissociative attachment should play an important role in a gas mixture containing HCl.  Fig. 1 shows cross section of dissociative attachment to HCl.

Figure 1. Cross section of dissociative attachment to HCl. Red solid line - Semiclassical calculation. Blue dashed line - Mandelshtam V.A.at al. Phys.Rev. A. 1994. V.50. P.2764
Vibrational excitation of SnI.

SnI is promising but not well explored molecule, so the result of analysis of SnI is new and rather important.   It is possible to demonstrate, that 3П and 1П states of the  resonance  SnI- play most important role in vibrational excitation of SnI. Figure 2 shows cross section of vibrational excitation of SnI. The result of semiclassical calculation is compared with the result of quantum-mechanical method.

Figure 2. Cross section of vibrational excitation of SnI. Red solid line - 3П, quantum-mechanical method. Blue solid line - 3П, semiclassical method. Green dashed line - 1П, quantum-mechanical method. Violet dashed line - 1П, semiclassical method.

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