There are two specific aims. The first is to build and develop a new type of Fourier transform mass spectrometer (FTMS) that utilizes a permanent magnet and an external ion source. Samples are ionized in the source by cesium bombardment liquid secondary ion mass spectrometry, and the ions are extracted from the source and transported to a FTMS analyzer cell. Three stages of differential pumping separate the cell from the ion source so that high mass resolution and high detection sensitivity can be achieved.
The second aim i s to study laser photodissociation of biomolecules and to develop it as a practical method for elucidating ion structures. The analytical scheme involves ionizing a sample in an external ion source and injecting the ions into the FTMS analyzer cell. Once the ions are in the analyzer cell they are irradiated with ultraviolet light from an excimer laser and caused to dissociate. The parent ions are stored in the analyzer for several seconds and can be exposed to many laser pulses, if necessary, to enhance the yield of daughter ions. At the end of the laser irradiation period a complete mass spectrum of the daughter ions is obtained. More structural information can then be obtained by isolating a particular daughter ion in the analyzer cell and fragmenting it further with additional laser pulses to produce granddaughter ions. Our goal is to understand the photodissociation process and to develop new technology for making it a sensitive (picomoles) and rapid means for structure elucidation.
