1. Fragmentation of Organic Molecules Desorbed from a Surface using Secondary-Ion Mass Spectrometry Alger Pike Nicholas Winograd

3. SIMS in Combinatorial Chemistry An optical image of a bead-holder specially fabricated for 60  m polystyrene beads (capacity: 10,000 beads/cm 2 ) The TOF image of Sasrin-Biotin beads loaded into the bead-holder. The molecular mass of biotin 245.3 amu is shown in green. R. M. Braun, A. Beyder, J. Xu, M. C. Wood, A. G. Ewing and N. Winograd, Anal. Chem. 71, 3318 (1999).

5. Types of Fragmentation 1) Direct Desorption 2) Desorb then Fragment 3) Ion-Beam Induced

6. The ARTOF-SIMS Machine

7. ARTOF-SIMS Sample Manipulator a) Azimuthal Rotation: Sample rotates like the hands of a clock, around the center of the crystal. b) Polar Rotation: Sample rotates like a revolving door, around the axis perpendicular to the azimuthal axis.

8. Ion Trajectories

9. Simulation Parameters

10. Simulation Results

11. Simulation vs. Real

12. Machine Automation

14. Controllable Parameters

15. CD 3 S-Cu (100): The Model System 1) Chemisorption to a four-fold hollow 3) No domains 2) No tilt angle due to short R group 4) Simplified mass spectra Imanishi, S. Takenaka, T. Yokoyama, Y. Kitajima and T.Ohta J. PHYS. IV FRANCE 7 (1997)

16. FCC (100) Surface 1) Red atom is an ejecting atom 2) Blue atoms are blocking atoms 3) SIMS yield decreases with blocking

17. Azimuthal Distribution of Cu(100) 50 0

18. 1200 L CD 3 SH on Cu(100) High Mass

19. 1200 L CD 3 SH on Cu (100) Low Mass

20. Overall Fragmentation of CD 3 SH (total fragments signal) (total monolayer signal) F =

21. Direct Desorption Fragmentation Low energy cascade that desorbs an ion which does not have enough energy to fragment.

22. Direct Desorption Fragmentation

23. Fragmentation After Desorption High energy cascade leads to desorbed species which have enough energy to further fragment.

24. Fragmentation After Desorption

25. Ion-Beam Induced Fragmentation The ion beam directly breaks a bond which causes desorption of the fragment into vacuum.

26. Ion-beam Induced Fragmentation (fragment signal) (total monolayer signal) C =

27. Two-Body Model Simulation

28. Ion Trajectories at 35 º Incidence Angle

32. Further Evidence for CD 3 + Formation XSCD 3 +  XS + CD 3 +

33. Image Potential

34. Ion Profile Above Extraction Plate