Transmission secondary ion mass spectrometry using 5 MeV C60+ ions

Track Date and time Hall Duration
Invited Lectures Monday, 15. June 2015., 13:30 Orhideja Hall 30’

Kaoru Nakajima  (1), Nagano Kengo (1), Kazumasa Narumi (2), Yuichi Saitoh (2), Koichi Hirata (3), Kenji Kimura (1)

  1. Kyoto University
  2. JAEA
  3. AIST

There has been an increasing demand to extend accessible mass range in secondary ion mass spectrometry (SIMS) particularly for biological and biomedical molecular imaging.  During the past two decades, various kinds of large clusters, such as C60 ions, argon gas cluster ions, water cluster ions, and metal cluster ions have been used as primary ions.  It was shown that these cluster ions enhance emission of intact large molecular ions compared to monatomic ion bombardment. In SIMS, secondary ions emitted from a sample in the backward direction with respect to the direction of a primary ion are generally measured. 

If a specimen of a self-supporting thin film is used, the secondary ions emitted in the forward direction upon transmission of the primary ions can also be measured.  So far, there have been only few studies about the transmission SIMS.  Boussofiane-Baudin et al found small enhancement of secondary ion yield in the forward direction compared to the backward direction [1].  The origin of the enhancement was suggested to be the larger stopping power at the exit surface due to higher charge states achieved during the passage.  In this presentation, we demonstrate that large enhancement of the secondary ion yield of intact biomolecules can be achieved by combining the cluster ions (5 MeV C60+) with the transmission SIMS [2].

We measured secondary ions emitted in the forward direction from phenylalanine amino acid films deposited on self-supporting amorphous Si3N4 films.  We found significant enhancement of the intact phenylalanine ion yield and large suppression of fragment ions compared to the backward direction. The origin of the observed enhancement and suppression will be discussed in the conference.  

[1] K. Boussofiance-Baudin, A. Brunelle, P. Chaurand, S. Della-Negra, J. Depauw, P. Hakansson and Y.Le Beyec, Nucl. Instr. and Methods in Phys. Res. B, 88 (1994) 61.
[2] K. Nakajima, K. Nagano, M. Suzuki, K. Narumi, Y. Saitoh, K. Hirata, and K. Kimura, Appl. Phys. Lett. 104 (2014) 114103.