Measurements of secondary ions emitted from organic compounds bombarded with large gas cluster ions

We propose to use cluster ions that are much larger than the molecular ions as primary ions for organic secondary ion mass spectrometry. Incident Ar cluster ion beams with energies from 10 to 20 keV and a mean size of about 1000 atoms/cluster were used. Secondary ions were measured for a thin arginine film target (200 nm) bombarded with large Ar cluster ions using a time-of-flight technique. Molecular ions of arginine and characteristic fragment ions were detected with high sensitivity. When large Ar cluster ions such as Ar-1500 were incident on the arginine target, molecular ions of arginine were detected with little fragment ions. This indicates that large cluster ions can ionize arginine molecules without damaging them. (c) 2006 Elsevier B.V. All rights reserved.