The Mechanism of the Argon Emission Continuum in the Vacuum Ultraviolet. I

The spectral intensity, I em , of the microwave excited continuous emission in molecular argon has been investigated from 1 060 to 1 450 Å as a function of pressure (p Ar ) with the result:[Formula: see text]The Ar 2 continuum, like Xe 2 , Kr 2 , and Ne 2 (X 2 ), exhibits a sharp short wavelength limit corresponding energetically to the 3p 5 4s 3 P 0 resonance configuration and two intensity maxima at 1 080 and 1 265 Å. The integrated intensities of the rare-gas continua compare as follows:[Formula: see text]with (I em ) Ne expected to be weaker still. The pressure dependence and the short wavelength limit suggest a two-body collision process involving 3 P 0 atoms as the controlling step to produce [Formula: see text] molecules responsible for the continuum.Although the lifetimes of the 3 P 0 atoms do play a kinetic role in the continuum production, it is concluded that the molecular transition probabilities, [Formula: see text] predominate and decrease, as expected in the direction Xe 2 * to Ne 2 * in the approach (weaker spin-orbit coupling) to Hund's case b.