1. CEFITEC, Departamento de Física, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica 2829-516, Portugal
2. School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, U.K.
3. Instituto de Física da Universidade de São Paulo, Universidade de São Paulo, São Paulo 05508-900, Brazil
4. Department of Chemistry and Science Institute, University of Iceland, Dunhagi 3, Reykjavik IS-107, Iceland