Coherent population trapping involving Rydberg states in xenon probed by ionization suppression T. Halfmann, K. Böhmer, L. P. Yatsenko, A. Horsmans and K. Bergmann Eur. Phys. J. D, 17 1 (2001) 113-123 Published online: 15 October 2001 DOI: 10.1007/s100530170044