1. Department of Physics, SCFAB, Stockholm University, SE-106 91 Stockholm, Sweden, Air Force Research Laboratory, Space Vehicles Directorate, 29 Randolph Rd, Hanscom AFB, Massachusetts 01731, Institute of Physics, Swietokrzyska Academy, 25-406 Kielce, Poland, and Manne Siegbahn Laboratory, Stockholm University, SE-104 05 Stockholm, Sweden