1. Centre for Astrophysics and Planetary Science, School of Physics and Astronomy, University of Kent, Canterbury CT2 7NH, UK
2. Institute for Nuclear Research (Atomki), H-4026 Debrecen, Hungary
3. Centre for Interstellar Catalysis (InterCat), Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus, Denmark
4. School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, UK
5. INAF Osservatorio Astrofisico di Catania, I-95123 Catania, Italy
6. Astronomical Institute, Slovak Academy of Sciences, SK-059 60 Tatranská Lomnica, Slovakia