1. Department of Physics and Technology, University of Bergen, P.O. Box 7803, NO-5020 Bergen, Norway
2. Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747AG Groningen, The Netherlands
3. Christian Michelsen Research AS, P.O. Box 6031, NO-5892 Bergen, Norway
4. ProAnalysis AS, P.O. Box 2619, NO-5836 Bergen, Norway