At the FOM Institute "Rijnhuizen" a new FEL light source is presently under development, which is dedicated to fundamental research of the structure and dynamics of (bio)molecules, clusters, and nano-particles demanding extremely high luminosity. This Free Electron Laser for Intra-Cavity Experiments (FELICE) is designed to generate pulsed infrared radiation, tunable in the region of 3-100 mum, which is often referred to as the 'molecular fingerprint' region. The temporal structure of the optical beam will consist of few-microseconds long, 1 GHz bursts of ps-micropulses, which are repeated at 10 Hz. FELICE should allow intra-cavity experiments with optical beam energies in the interaction point of some 10 J in a few microseconds, which is a factor of 100 higher than currently available for the users. Two permanent intra-cavity set-ups are planned: a Fourier Transform Ion Cyclotron Resonance mass spectrometer (FT-ICR) with appropriate ion sources and a pulsed molecular beam (PMB) set-up coupled with a mass spectrometer. (C) 2003 Elsevier Science B.V. All rights reserved.