Hornbeck-Molnar process

In mercury vapor irradiated by the 2537-A mercury resonance line, ionization was observed91 and later attributed92 to the AI process (IV.2). Since then AI was reported for a large number of systems.93 Especially the homonuclear AI, also called Hornbeck-Molnar process,94... 

The Hornbeck-Molnar process (13) is indicated by the linear relation obtained when the ratio Ar2 /Ar is plotted against reciprocal pressure. This has been observed by Pahl for the positive column of a dc discharge of Ar. The variation in electron energy with pressure is not expected to be important in this case because the energy levels of the excited argon lie close to the ionization continuum. 

The only heteronuclear diatomic ion of the inert gases reported in electrical discharges is HeNe". It appears to be formed by the Hornbeck-Molnar process below approximately 1 Torr in the positive column of helium-neon discharges " and by a three-body process above approximately 7 TottP ... 

The diatomic ion Ar2 in an rf discharge of argon at 3 Torr appears to be formed by a Hornbeck-Molnar process at low rms voltages of the rf field and by a three-body process at high rms voltages. ... 

Somewhat akin to ion-molecule reactions is a process first identified by Hornbeck and Molnar (45) for forming the rare gas diatomic ions. Hornbeck and Molnar observed diatomic ions of all the rare gases and found their intensities to vary as the square of the pressure. The appearance potentials of the diatomics proved to be 0.7 to 1.5 e.v. below the ionization potentials of the corresponding atom, and hence the diatomic ions were not derived from atomic ions. As a consequence, they proposed that excited atoms formed by electron impact reacted upon collision with a neutral atom to form a molecular ion and eject an electron, thus ... 

In 1951, Hornbeck and Molnar successfully determined that the formation of the diatomic rare-gas ions occurred by a chemi-ionization process in which an electronically excited atom reacts with an atom in the ground state to form an ion i.e.. 

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