NUCLEAR INSTRUMENTS AND METHODS I32 (1976) 439-444; © NORTH-HOLLAND PUBLISHING CO. LINE SHAPE MEASUREMENTS OF ATOMS SPUTTERED FROM POLYCRYSTALLINE Cu, Zn AND A! BY 300 keV Ar + BOMBARDMENT* R. HIPPLER, W. KRI~GER, A. SCHARMANN and K.-H. SCHARTNER L Physikalisches Institut der Justus Liebig-Universit?it, 63 Giessen, Germany The line shape of atomic transitions of excited Cu, Zn, and AI atoms sputtered from polycristalline metal and from surface- coated Zn and AI by the bombardment with 300 keV Ar + ions has been measured. The influence of radiationless de-excitation processes on the line shape has been studied. The experimental results are compared with a single collision model introduced by van der Weg and Bierman 7) for Ar + bombardment of Cu. 1. Introduction Ion bombardment of solids results in the emission of light which can be attributed to radiation from sputtered or backscattered particles l-7) or - mostly in the case of semi-conductors - to emission by the solid itself s). For the escape of particles in an excited state radiationless processes like resonant electron transfer and Auger processes are determiningg). The resonance ionization in connection with the knowledge of the energy levels of the bombarded solid is very capable to explain intensity ratios of atomic lines emitted during the ion bombardment of metals or of their oxides, the influence of oxygen gas on the intensity l°) and the velocity spectrum of the emitting particlesll). Re- sonance ionization is also used in the discussion of line shapes which have been measured in high resolu- tion studies of the light emission from backscattered or sputtered particlesT). Measurements of this kind even allow to obtain quantitative data for the pro- bability of the radiationless decay. Line shape mea- surements of excited target atoms have so far been published only by Van der Weg and Bierman v) for Ar-bombardment of Cu and by White et al. 12) for Si and SiOz. The latter authors for the first time showed a change in line shape for different target conditions though this has already been mentioned by Van der Weg and Bierman for Cu and CuzOV). But having no Si reference line only a change of the line width and the integral of the line can be taken from the paper of White et al)Z). We now carried out some measurements with the aim of investigating the effect of the radiationless decay especially on the line shape. We used AI und A120 3 targets, as for these the effect of the surface conditions on the total intensity of atomic AI lines has been studied~°), and Zn targets, as for Zn there are excited atomic levels which lie above or below the Fermi level of Zn and therefore are in a similar way suitable for the study of resonance ioniza- tion as the levels of A1 are under the change of the surface conditions. We also used a Cu target to have a comparison with the results of Van der Weg and Bierman 7) who gave an explanation for their observed line shape under the assumption of single collisions occurring between the impinging ions and surface atoms. 2. Apparatus The measurements were done using mass-analyzed beams of 300 keV Ar + ions. The ions were produced in the radio-frequency ion source of a I MeV Van de Graaff accelerator and directed on to Al, Cu, or Zn targets, mounted under an angle of 45 ° with respect to the ion beam (see fig. 1). The base pressure inside the target chamber was maintained to 1 × l0 -8 torr by means of two ion-getter pumps. Light emitted from sputtered target atoms was observed through a saphir window with the observation direction parallel to the surface normal; no other observation angle with respect to the ion beam was allowed due to the con- struction of the target chamber. The light was dispersed by a Leiss monochromator; the distance between monochromator entrance slit and target was about 60 cm. The monochromator is equipped with a grating (1800 lines/mm; linear dispersion 1 mm/18 A; focal length 30 cm), which allows with slit widths of 0.05 mm Ar* 1,5 ° ~5o~a ~ Monochromotor * Dedicated to Prof. Dr lng. E.h.W. Hanle on the occasion of Fig. 1. Schematic experimental set-up showing target orientation his 75th birthday, and observation direction. VII. PHOTON EMISSION