Electron Capture into Excited States for Al⁸⁺ + H₂ Collisions at 3 keV/amu

Extract

The MINIMAFIOS ECR source at Grenoble has recently produced stable beams of highly charged Al. We have studied electron capture into excited states for Al⁸⁺ ions extracted at 10 kV colliding with an H₂ molecular target under single collision conditions. Using a grazing incidence spectrometer covering the region 250 Å to 1100 Å, we have made a relative intensity measurement of the radiative decay from excited (nl) states of Al⁷⁺ following the charge exchange collision. The Al⁷⁺ spectra show known transitions from the ls²2s2p³ excited state. We discuss the presence of the ls²2s2p²(⁴P) metastable state in the incidence Al⁸⁺ beam. The spectra also show many transitions which up to now are unidentified, in particular transitions for the wavelength region between 300 and 400Å and that between 600 and 700Å. To identify the transitions, we compare our spectrum with preliminary theoretical wavelengths calculated using the multiconfiguration Dirac-Fock method including transitions from n = 3, 4 and 5. These preliminary results reveal transitions from n = 5 to 4 for the observed spectra in the 600Å region and transitions from n = 4 to 3 for the observed spectra in the 300Å region.