Energy-transfer processes in decaying helium-copper gaseous plasmas

The time dependences of 35 Cu II energy levels between 15.96 and 24.62 eV were studied using light emission and absorption spectroscopy during the afterglow of a sputtered He-Cu hollow cathode discharge. By measuring the decay of the Hem(2S3) and Cu(4sS122) densities, it was possible to determine the helium species [He+, He2+, Hem(2S3), and He2m(au+3)] responsible for production of the Cu II states. The Cu II levels between 22.7 and 24.62 eV are produced, either directly or by cascading, by charge exchange between He+ and Cu. The Cu II levels between 15.96 and 21.41 eV are produced by charge exchange between He2+ and Cu. No evidence was found for the production of Cu II states by the Penning ionization of Cu by Hem(2S3) or He2m(au+3). A value of 43010 cm2 sec-1 Torr was measured for the diffusion coefficient of Cu(4sS122) in helium. The time dependence of the sputtered Cu(4sS122) radial density profile was also investigated theoretically during the discharge sequence.