1. Laboratory for Astrophysics, Leiden Observatory, Leiden University, P.O. Box 9513, NL–2300 RA Leiden, The Netherlands
2. Fine Mechanical Department, Leiden Institute for Physics Research (LION), Niels Bohrweg 2, NL–2333 CA Leiden, The Netherlands
3. Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 3, D–07743 Jena, Germany
4. Institute for Theoretical Chemistry, University of Stuttgart, D–70569 Stuttgart, Germany
5. School of Electronic Engineering and Computer Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
6. Leiden Observatory, Leiden University, P.O. Box 9513, NL–2300 RA Leiden, The Netherlands