1. Physique Atomique et Astrophysique, Université de Mons, B-7000 Mons, Belgium
2. Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing, Université libre de Bruxelles, CP160/09, B-1050 Brussels, Belgium
3. IPNAS, Université de Liège, Sart Tilman, B-4000 Liège, Belgium
4. Institute Hebei Key Lab of Optic-electronic Information and Materials, The College of Physics Science and Technology, Hebei University, Baoding 071002, China