We cordially invite you to attend he 23rd International Symposium on Ion Atom Collisions (ISIAC 2013), which will be held at Institute of Applied Physics and computational Mathematics in Beijing, China. The conference will start on Friday July 19th, and finish on Monday July 22nd, 2013. This is a three-day (including 2 days of meeting and 1 day tour) biennial satellite meeting taking place right before ICPEAC and usually attracting about 50-80 participants from all over the world. It gives the participants an opportunity to present and exchange detailed information at a smaller specialized meeting set in a congenial and personalized atmosphere. The symposium covers all ion-atom collision phenomena including excitation, ionization and capture reactions from sub-thermal to relativistic velocities, and interactions of ions with surfaces, molecules and clusters, as well as the evaluation and applications of atomic and molecular database. The scientific program will include invited talks and one poster session.