This Small Business Innovation Research Phase I (SBIR) project will test Cesium Iodide cluster ion beams as an alternative to lasers for desorbing bioions from a MALDI ((Matrix Assisted Laser Desorption Ionization) matrix. This offers the possiblity of performing the post source decay tandem mass spectrometry on an event by event basis, making possible the application of coincidence techniques which allow specific correlations to be made between metastable parent ions and their ionic fragments. This is an anaolgy to what has already been demonstrated for 252Cf fission fragment plasma desorption mass spectroscopy of bioions. Thus post source decay becomes a true MS/MS technique. There is also the possiblity that the use of cluster ions can increase the fragmentation and the degree of metastability of the desorbed bioions compared to using a laser. If so, the cluster deorption technique may be more suitable than lasers for imaging biomolecules on materials such as polymers or tissue slices. This Phase I project proposes to develop a cheap and reliable cluster ion source for MALDI. At the conclusion of Phase II, this ion source could be combined with a curve field reflector TOF mass spectrometer and marketed as a new approach to post source decay measurements.<br/><br/>The commercial applications of this project will be in the area of biomolecular mass spectrometry.