Ambient Pressure Mass Spectrometry at the Sub Micron Scale

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This proposal aims to develop a new ambient pressure mass spectrometry imaging system. It will use a beam of ions accelerated to MeV potential energy - velocities of the order of 5% the speed of light or less. The beam will be focussed using a set of quadrapole magnetic lenses to less than a micron in size and will be passed out of the vacuum system through a 100nm thick silicon nitride window into air where it will be able to travel between 0.5-1.0cm before stopping. A sample placed in front of this beam of ions will be sputtered (eroded) by the interaction of the ions with the electrons in the system (electronic energy loss). Previous experiments in vacuum have demonstrated that if the sample is a molecular material it is possible to extract large (~45kDa) molecular species from the surface and that these can be detected in a Time of Flight mass spectrometer to determine their molecular mass. Fragments that are removed at the same time give indications about the bonding arrangements of the molecules sputtered and can be used to determine the probable molecular arrangement.The beam itself can be raster scanned using an electrostatic field so that a molecular map of the surface of the material can be determined at the micron scale. The ions as they enter the surface of the material are moving fast enough that they will also cause electrons in the outer shells of the atoms that they pass to become exited and in relaxing back will give out a characteristic X-ray. These X-rays can also be collected and analysed using a technique known as Partical Induced X-ray Emmision (PIXE) to give trace element maps as well.This will be the worlds first scanning mass spectrometer capable of imaging at the sub micron scale in air.Applications for this equipment range from forensics to biomedicine taking in geology and the environment as well as helping to understand the origins and manufacture of art and archeological remains. These applications will be encouraged over the period of the project.