Abstract
The possible use of level-crossing spectroscopy to study properties of excited states generated by gas excitation of fast ionic beams has been investigated. With a 20-400 keV Be+ beam excited by means of helium gas, radiative lifetimes of 2D and 2F levels in Be II have been determined together with the fine-structure separation of the 5f 2F level in Be II and the hyperfine coupling constant for the 2s3d 1D level in Be I and the 2p 2p level in Be II.