Excitation transfer collisions electronic

A-B relative or external motion undergo free-free transitions (E., E. + dE.) (Ej Ej+ dE within the translational continuum, while the structured particles undergo bound-bound (excitation, de-excitation, excitation transfer) or bound-free (ionization, dissociation) transitions = (a, 3) ->/= (a, (3 ) in their internal electronic, vibrational or rotational structure. The transition frequency (s ) for this collision is... 

The differences between x-ray and electron excitation must obviously stem from differences in the interaction of x-rays (1.11) and of electrons (1.4) with matter. Electrons are retarded rather quickly when they strike a sample, and they lose much of their energy in classical collision processes (4.1). Because electrons transfer their energy so rapidly, the critical thickness (Equation 6-8) for electron excitation is very much less than we saw it to be for x-ray excitation a.calculation based on experiments on a variety of materials53 gives 1CT3 cm (105 A) as a good value for the depth to which 50-kv electrons penetrate aluminum, and bears out the previous statement. Because the energy of every electron decreases as it penetrates, the x-ray excited by any electron will be of... 

Ne is metastable neon produced by electron impact. Ne transfers its excitation to hydrogen molecules. The hydrogen molecules participating in these energy transfer collisions are produced in highly excited preionized states which ionize after a time lag sufficient to permit the initial neon and hydrogen collision partners to separate. The hydrogen ion is formed in the v = 5 or 6 quantum states and reacts with a second neon... 

Figure 28. Electron spectrum for collision system He -Kr at various collision energies. Broad distribution at low electron energies is a result of Penning ionization, and narrow peaks arise from atomic autoionization of krypton following excitation transfer from He to Kr.77...

The branching ratio is 1 1000 in favor of the ground state. The beam is scattered from a second supersonic beam, and the electronically excited atoms are detected. As excitation transfer can occur during the collision (e.g., He + Ne— He + Ne ), a second quench lamp is sometimes installed in front of the detector, to enable study of the energy-transfer process separately. 

Mercury may be easily excited to the 6 aP2 state by 2537-A radiation or by electron impact, and the excitation energy may be removed partly or totally in collisions with unexcited atoms or molecules. It is generally recognized that collisions with noble-gas atoms do not result in excitation transfer to the 6 3P0 metastable state or in quenching to the 6 S, ground state [90-92] and that such processes can be accomplished only in collisions with molecules... 

Frish and Kraulinya and, most recently, by Czajkowski, Skardis, and Krause [71] and Czajkowski, Krause and Skardis [96]. Frish and Bochkova [97, 98] studied excitation transfer from the 6 aPr and 6 aP0 mercury atoms excited by collisions with electrons in a discharge, to various states in sodium. Kraulinya [99] optically excited the Hg(6 aPJ state and followed the excitation transfer to sodium by monitoring the intensities of the collisionally sensitized sodium lines. Her results which are quoted within 30% — 50% are summarized in Table 4.5 and are compared with the cross sections determined by Czajkowski, Skardis and Krause [71], The considerable discrepancies between the two sets of results are apparently due to errors arising from the trapping of mercury resonance radiation [100, 28] which must have particularly affected Kraulinya s results, and from the uncertainty in the determination of the mercury and sodium vapor densities in the binary mixture. 

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