Slow ammonia molecules in an electrostatic quadrupole guide T. Junglen, T. Rieger, S. A. Rangwala, P. W.H. Pinkse and G. Rempe Eur. Phys. J. D, 31 2 (2004) 365-373 Published online: 28 September 2004 DOI: 10.1140/epjd/e2004-00130-3