A pulsed atom laser derived from a Bose-Einstein condensate is used to probe a second target condensate. The target condensate scatters the incident atom laser pulse. From the spatial distribution of scattered atoms, one can infer important properties of the target condensate and its interaction with the probe pulse. As an example, we measure the s-wave scattering length that, in low energy collisions, describes the interaction between the |F = 1, m F = −1 and |F = 2, m F = 0 hyperfine ground states in 87 Rb.Controlled collisions for multiparticle entanglement of optically trapped atoms," Nature (London) 425, 937-940 (2003). 16. C. Samuelis, E. Tiesinga, T. Laue, M. Elbs, H. Knöckel, and E. Tiemann, "Cold atomic collisions studied by molecular spectroscopy," Phys. Rev., "Quantum scattering of distin-guishable bosons using an ultracold-atom collider," Phys. Rev. A 75, 020701(R) (2007). 22. Due to the rf ouput-coupling process we cannot avoid a weak density cloud of atoms in the |2,1 state. In the numerical analysis, the position of these atoms during the scattering process is approximated to be identical to the position of the source condensate. 23. Th. Busch, M. Köhl, T. Esslinger, and K. Mølmer, "Transverse mode of an atom laser," Phys. Rev. A 65, 043615 (2002). 24. M. J. Bijlsma and H. T. C. Stoof, "Coherently scattering atoms from an excited Bose-Einstein condensate," Phys. Rev. A 62, 013605 (2000). 25. Uffe V. Poulsen and Klaus Mølmer, "Scattering of atoms on a Bose-Einstein condensate," Phys. Rev. A 67, 013610 (2003).