Spectral Evolution During Ultracold Neutron Storage A. Steyerl, S.S. Malik, P. Geltenbort, S. Neumaier, V.V. Nesvizhevskii, M. Utsuro and Y. Kawabata J. Phys. III France, 7 10 (1997) 1941-1954 DOI: 10.1051/jp3:1997233