The dynamics of electron 'bubble' formation upon excitation of the A(3ssigma) Rydberg orbital of NO in solid Ne was investigated by means of ferntosecond pump-probe spectroscopy. We observe an ultrafast expansion of the bubble, followed by a vibrational recurrence in similar to1.4 ps. The overall dynamics is slower than in the heavier argon solid. Molecular dynamics simulations show that this results from the collective motion of several shells around the excited impurity, as a result of the nature of the excited NOA-Ne and the Ne-Ne potentials. Quantum effects play a negligible role in the dynamics. (C) 2002 Elsevier Science B.V. All rights reserved.