The Far Ultraviolet Emission of a Helium Discharge Source Studied by Photoelectron Spectroscopy J. Barrie Peel La Trobe University, Bundoora. Victoria 3083.Australia Ellak I. von Nagy-Felsobuki The University of Newcastle, Newcastle, N. S. W.,2308,Australia This article describes an unusual application of the technique of the ras phase ultraviolet photoelectron spectroscopy-of free atoms. Instead of using a single wavelength of ionizing radiation to probe the various valence orbital levels of a tareet atom. which is the usual obiect of the nhotoelectron experiment, a single ionization of a simple target atom is used to reveal the varietv of ionizine waveleneths in the emission line spectrum of the gas discharge source. Photoelectron (PE) mectrosconv has become an important technique i n the study of eiectron structure of liquids and solids (1-3). It is included in many undergraduate courses in physics and chemistry (4, 5).Articles in this Journal have described the experimental and theoretical basis of the gas-phase photoeleciron experiment (6-9). The two main areas of photoelectron spectroscopy are ultraviolet ohotoelectron snectrosconv where UV radiation is . . (UPS) . u i d fur \,alenceelcctnm ionization i~ndX-rayphorwlccrrun spectroscopy (XI'S) u,hrrr core elecrri~nionimtion is studied. The basic photoelectron experiment for an atomic target gas is governed by the Einstein equation, KE=hu-IE
(1)
where KE is the kinetic energy of the electron of ionization enerev IE eiected hv radiation of freauencv u. Uit&&t PI? s&ctromctrrs are basrd on the pio~iiwing work of Turner and cu-workers ( I , 10) where the radiatmn source t i an rlectricaldisrharge in helillm, which under vnrvingrondirions prodltres mainly the He([)
