1. Instituto de Investigaciones Físicas de Mar del Plata (IFIMAR), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata & CONICET, 7600 Mar del Plata, Argentina
2. Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
3. Yale Quantum Institute, Yale University, New Haven, Connecticut 06520, USA
4. Department of Physics, University of Connecticut, Storrs, Connecticut, USA
5. Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA
6. Departamento de Física ``J. J. Giambiagi'' and IFIBA, FCEyN, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina