Cationization of organic molecules under keV and MeV primary ion bombardment

The present work reports on cationization characteristics of organic molecules in alkali metal environment. Samples of arginine and polyethylene glycol polymers with average masses of 600, 1000 and 1500 were mixed with sodium- and potassium trifluoroacetate of various concentrations, and analyzed through secondary ion mass spectrometry. Bombardment proceeded with ions within both keV and MeV energy domains. Added salts positively affected the secondary ion yield through attachment of Na or K to organic molecule. Ionization differences between swift (MeV) ions and cluster ions, commonly used for secondary ion mass spectrometry analysis, were studied for arginine and PEG 600. While for arginine, secondary ion yield enhancement was only by a factor of 2, when analysing with MeV ions, and no enhancement was observed with keV Bi3 clusters, all polyethylene glycol samples showed increase of the secondary ion yield by factors between 3 and 40, depending on the amount of potassium or sodium that was mixed into the matrix. Additionally, higher amounts of salts also resulted in decreased fragmentation probability for organic molecules, reducing the intensities of specific fragments by more than two orders of magnitude.