Nuclear Physics A 759 (2005) 43–63 Quasi-free scattering with 6,8 He beams L.V. Chulkov a,b,∗ , F. Aksouh a,c , A. Bleile a , O.V. Bochkarev a,b , D. Cortina-Gil d , A.V. Dobrovolsky e , P. Egelhof a , H. Geissel a , M. Hellström a , N.B. Isaev e , O.A. Kiselev e,f , B.G. Komkov e , M. Matoš a , F.N. Moroz e , G. Münzenberg a , M. Mutterer g , V.A. Mylnikov e , S.R. Neumaier a , V.N. Pribora a,b , D.M. Seliverstov e , L.O. Sergeev e , A. Shrivastava h , K. Sümmerer a , S.Yu. Torilov i , H. Weick a , M. Winkler a , V.I. Yatsoura e a Gesellschaft für Schwerionenforschung (GSI), D-64291 Darmstadt, Germany b Kurchatov Institute, RU-123182 Moscow, Russia c University of Leuven, B-3001 Leuven, Belgium d Universidad Santiago de Compostela, E-15706 Santiago de Compostela, Spain e Petersburg Nuclear Physics Institute, RU-188350 St. Petersburg, Russia f Institut für Kernchemie, Universität Mainz, D-55099 Mainz, Germany g Institut für Kernphysik, Technische Universität, D-64289 Darmstadt, Germany h Bhaba Atomic Research Center, 400085 Mumbai, India i St. Petersburg State University, RU-198904 St. Petersburg, Petrodvorets, Russia Received 4 March 2005; received in revised form 29 April 2005; accepted 13 May 2005 Available online 8 June 2005 Abstract This paper presents the results of experimental investigations of (p,pn), (p,pα) and (p,p 6 He) reactions with relativistic 6 He and 8 He beams impinging on a hydrogen target. Information on the structure of extremely neutron-rich nuclei was obtained by using the unique characteristic of quasi-free scattering processes and inverse kinematics. For the first time, momentum distributions of complex clusters inside 6 He and 8 He were measured. Spectroscopic factors for valence neutrons, α- and 6 He clusters were deduced from the experimental data. They demonstrate that the filling of the * Corresponding author. E-mail address: l.chulkov@gsi.de (L.V. Chulkov). 0375-9474/$ – see front matter  2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysa.2005.05.148