Comparison of MeV monomer ion and keV cluster ToF‐SIMS

Abstract

Recent results [1] show the potential of using monomer primary ions accelerated to several MeV with a tandem accelerator to achieve the necessary secondary ion yields to image large (above 1 kDa) molecules with submicron lateral resolutions. The Surrey ion Beam Centre (Surrey IBC) has designed a time-of-flight secondary ion mass spectrometer (ToF-SIMS) combined with a 2 MV Tandem accelerator to investigate the characteristics of the desorption of secondary ions by the impact of fast, heavy, primary ions. The application of this MeV-ToF-SIMS technique is intended to eventually image biomolecules in the subcellular regime without the need for matrix application associated with other mass spectromery techniques, such as Matrix Assisted Laser Desorption ionisation (MALDI). A discussion is given to point out the merits of using a combination of Particle-Induced X-ray Emission Spectrometry (PIXE) and Rutherford Backscattering (RBS) with the MeV-ToF-SIMS measurement to improve quantification and sensitivity of this surface analysis technique. We also present data from highly focused MeV primary ions to directly compare results obtained using keV cluster-SIMS to measure various biological materials using ToF-SIMS through sputtering in both the nuclear and electronic stopping regimes. Our findings show that the mass spectra obtained with MeV ions in the electronic stopping regime show similarities to those acquired with more conventional keV ion beams (e.g. Bi + , Bi 3 + , Bi 5 + and C 60 + ). MeV-ToF-SIMS has the potential for becoming a widely used quantitative surface analysis technique in the many ion beam analysis facilities already conducting-high energy ion beam analyses.

Secondary ion and neutral mass spectrometry with swift heavy ions: Organic molecules

“…In this study, we report our initial experiments performed with this setup on organic films irradiated by 4.8 MeV/u gold ions. ToF-SIMS studies on molecular ion emission under SHI bombardment have been reported before, [10][11][12][13][14][15] indicating that electronic sputtering might be a possible strategy to "softly" desorb intact molecules with minimal amount of fragmentation. These experiments, however, have been conducted at lower kinetic energies where electronic and nuclear stopping are of comparable magnitude and, most importantly, were restricted to the ionic component of the sputtered material.…”

Submicron mass spectrometry imaging of single cells by combined use of mega electron volt time-of-flight secondary ion mass spectrometry and scanning transmission ion microscopy

“…[19][20][21][22][23] The main reason for this is that the ion microbeam pulsing (providing the start signal for TOF) requires rather high initial ion beam currents, which are delivered by the accelerator to the ion microprobe. 19,20 In the recently commissioned MeV TOF-SIMS setup at RBI, 21 the most commonly used primary beams are oxygen and silicon ions between 5 and 20 MeV. In order to obtain a sufficiently narrow pulse width (<10 ns), which is essential for high mass resolution, the primary ion microbeam current has to be greater than 100 pA.…”

Mass Spectrometry Imaging in Nanomedicine: Unraveling the Potential of MSI for the Detection of Nanoparticles in Neuroscience

“…This desorption mechanism occurs due to the electronic excitation of surface molecules when using high energy ions. 42,43 Although this new development shows great promise the use of MeV energy ions is limited to accelerator facilities and focusing of the energetic primary ion beam is challenging. As a result, its use is limited to carefully selected biological problems.…”