Affiliation: | a Instytut Fizyki, Polskiej Akademii Nauk, Al. Lotnikow 32/46, 02-668 Warszawa, Poland b LURE, Orsay and DRECAM-SRSIM, Saclay, France c II Institut fur Experimentalphysik, Universitat Hamburg, Luruper Chaussee 149, D-22761 Hamburg 50, Germany d Facultes Universitaires Notre-Dame de la Paix, LISE, 61 rue de Bruxelles, B-5000 Namur, Belgium |