1. Fragmentation of H2O molecule by slow, highly charged ions
Z.D. Pešić
R. Hellhammer
N. Stolterfoht
Hahn-Meitner Institut, Berlin, Germany
J-Y. Chesnel
CIRIL, Caen, France
B. Sulik
ATOMKI, Debrecen, Hungary

2. Motivation:
-fragmentation dynamics of multi-body systems
-test molecule for studies of biomolecules
-need for absolute cross section
Previous studies:
-most of studies done for diatomic molecules
-intensive coincidence studies by groups in Groningen and Bielefeld
Our studies:
-collision of H2O with keV Neq+ (q=3-9), Arq+ (q=5-13) and Xeq+ (q=9-25) ions
Our results:
-energy distribution of fragment ions
-strong charge state and angular dependence
-absolute cross section

3. Hahn-Meitner Institute, Berlin
Experimental set-up
Hahn-Meitner Institute, Berlin
Ion Spectrometer

4. Slow HCI (e.g. Ne9+) approaching a molecule
The energy of the fragment ions is governed by:
-Coulomb explosion (first order)
-momentum transfer to the molecule
-influence of the post-collision field of projectile

5. 21 keV Neq+, =135o

6. H+ + H+ + OQ+ H+ + H0 + OQ+ 21 keV Neq+
Peak b: H+ + OH- or H+ + H+ + O0
21 keV Neq+

7. Xe22+

8. 20 keV Ne9+, Ar13+ and Xe22+
 = 90o

9. keV Ne9+
=25o = 135o

10. keV Xe22+, =25o and 135o

11. 21 keV Neq+, =25o

12. Ne9+

13. Xe22+

14. Fragmentation to channel: H++H++O+
 Exp=(2±0.8)x10-14 cm2
Th= 1x10-14 cm2
Comparison with orbital promotion model
Reasonable agreement!!!!
Conclusions and Outlook:
-Energy and angular distribution of fragment ions
-Strong charge state dependence
-Significant post-collision interaction
-Absolute Cross Sections
Open questions:
-Fragmentation to 2 or 3 charged particles
-Identification of peak b