Time and Pressure Dependence of the Vacuum-Ultraviolet Radiation in Neon

A 250-keV electron accelerator was used to carry out time-dependent studies in neon gas at the wavelength of the ${}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ resonance line and the 850-Å continuum over a wide range of pressures, up to 1000 Torr. The resonance line decays exponentially with a lifetime that is governed predominantly by the escape of resonance radiation to the walls of the emission chamber and by three-body destruction of the resonance states. The main continuum near 859 Å comes to a maximum well after termination of the excitation pulse and then decays with a lifetime that is very long at low pressures. However, this lifetime decreases with increasing pressure at low and intermediate pressures and assumes a nearly constant value of 5.1 μsec at the highest pressures. From the time-dependent studies it is proposed that both ${}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ resonance states are converted to metastable molecular states by three-body collisions. The metastable molecules in turn may undergo two- and three-body collisions with ground-state atoms which convert them to radiative molecules that radiate the 850-Å continuum with a lifetime of about 5.1 μsec.