Ion source
Experimental stationat FEL focus
Ion trap
FLASHmonochromatorbeamline
Fragmentdetectors
VUV PHOTOFRAGMENTATION PATHWAYS OF COOLED HeH+ STUDIED AT FLASH
The TIFF experiment [3,4] – Trapped Ion Fragmentation at FLASH [1,2]
H. B. Pedersen1, L. Lammich1, B. Jordon-Thaden2, C. Domesle2, O. Heber3, J. Ullrich2, R. Treusch4, N. Guerassimova4, and A. Wolf2
HeH+ XUV photodissociation
1Department of Physics and Astronomy, Aarhus University, Denmark, 2Max-Planck-Institut für Kernphysik, Heidelberg, Germany , 3Dept. of Particle Physics, Weizmann Institute of Science, Rehovot, Israel, 4HASYLAB, DESY at Hamburg, Germany.
Ionsource
Quadrupole deflector
Separatormagnet
Focusing& steering
Ion beam preparation
4.2 kV
Diagnostics & collimation
DET 1
DET 2
FLASH beam
FLASH dump
Trapping and pulsing
Ion dumpFragmentdetection
Interactionregions
Key features
Photofragmentation of fast mass-selected, gas-phase molecular ions
Fast ion beam
• target preparation
• universal acces to all fragments, including neutrals
Ion trapping
• preparation/characterization of initial state
Momentum imaging
• Kinematically complete analysis of fragments -determining m/q, energy and emission angle
• Identification of electron proceses - electron spectrometry under development.
• Reaction microscope
Ion pulses
He
DET 2
DET 1
H+
Ion dump
FLASH pulses
Interaction regionElectrodes for biasing,deflection, trapping
Detection systemTime- and position sensitive,coincidence detection
HeH+ is a fundamental system
• Non-adiabatic interactions
• Astrophysics
• Neutrino mass measurements
• Ionic analog of H2
– e.g. dissociation in strong laser fields
XUV photodissociation of HeH+
• Dominating reaction channels ?He + H+ or He+ + H
• Dominating absorption states ?- versus -
• Dominating fragment states ?H(nl), He(1snl) – which n ?
• Importance of vibrational excitation ?
HeH+ + 32 nm
He+(1s) + H(nl)
[HeH+(/)]*
He(1snl) + H+
p
p
References
[1] W. Ackermann et al., Nature Photonics 1, 336 (2007)
[2] K. Tiedtke et al., New J. Phys. 11, 023029 (2009)
[3] H. B. Pedersen et al. , Phys. Rev. Lett. 98, 223202 (2007)
[4] H. B. Pedersen et al., Phys. Rev. A 80, 012707 (2009)
[5] H. B. Pedersen et al., Phys. Rev A 82, 023415 (2010)
[6] I. Dumitriu and A. Saenz, J. Phys. B 42, 165101 (2009)
[7] K. Sodoga et al., Phys. Rev. A 80, 033417 (2009)
Absorption states Angular distributions
HOT ions COLD ions (v=0) Theory [6]
He + H+ : - 30 2 % - 24 6 % ~ 30 %
- 70 2 % - 76 6 % ~ 70 %
He+ + H : - 38 3 % - 50 3 % ~ 15 %
- 62 1 % - 50 5 % ~ 85 %
Summary of results on HeH+ + 32 nm [5]
Reactions channels Imaging with biased interaction region
HOT ions COLD ions (v=0) Theory [6]
0.96 0.11 1.70 0.48 ~ 1.6
Final states - fragment excitation Final kinetic energy
HOT ions COLD ions (v=0) Theory
He(1snl) + H+ : n > 3 - 4 n > 3 - 4 ?
He+ + H(nl) : n > 3 - 4 n > 3 - 4 ?
He+ + H----------He + H+
Experimental results [5]
Imaging with a biased interaction region
He+ + H(nl)
Imaging with coincidence detection
He(1snl) + H+
Vibrationally hot and cold ions [5]
