Recombination Spectra of Atomic Ions and Electrons

Abstract

Method of enhancing recombination in a discharge tube.---Spectra were excited in a thermionic discharge tube containing a fine wire cathode completely inclosed by a cylindrical anode. When operated with low voltage and relatively high current and vapor pressure, high ion concentration and recombination of ions and electrons were favored.Photographs of recombination spectra of caesium and potassium.---Currents from 0.05 to 0.7 amp. in caesium vapor at pressures from 0.1 to 1 mm gave continuous bands extending to the violet from the limit $2{P}_{1}$ of the subordinate series, from the limit of the $F$ series and faintly beyond the $P$ series. The intensity of these bands is rapidly increased by increasing the vapor pressure or the current. Under these conditions the higher series lines are enhanced and the $F$ and $D$ series relatively intense. Lines near the limit become very diffuse and the forbidden series $1S\ensuremath{-}mD$ is excited. Potassium under similar conditions shows a strong band beyond the subordinate series.Spectrophotometer measurements in recombination spectra.---Intensities of the continuous spectrum were measured throughout the visible range. The intensity reaches a maximum slightly on the red side of the limits $2{P}_{1}$ and $3{D}_{2,3}$ and decreases regularly and rapidly on the violet side. The two peaks are of the same magnitude with the $P$ peak relatively greater at lower pressures. The intensity is proportional to the square of the current.The phenomena are qualitatively in accord with theory. The intensity distribution in the line spectrum indicates that there is a relatively high probability of recombination into levels of high quantum number giving radiation in the far infrared. Recombination into the normal level is relatively improbable.