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Instrumentation in the Molecular Physics Group

Instrumentation in the Molecular Physics Group. Presented by: Mats Larsson. Experimental research activities. Electron-driven molecular processes Ultrafast chemical physics Spectroscopy of clusters (Microwave induced chemistry) (Linear ion trap) (Biomedical imaging).

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Instrumentation in the Molecular Physics Group

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  1. Instrumentation in the Molecular Physics Group Presented by: Mats Larsson

  2. Experimental research activities • Electron-driven molecular processes • Ultrafast chemical physics • Spectroscopy of clusters • (Microwave induced chemistry) • (Linear ion trap) • (Biomedical imaging)

  3. Electron-driven molecular processes • The problem of producing quantum systems (i.e. molecules) in well defined states • How to produce ionized biological molecules in the gas phase • How to detect reaction products of electron-driven processes • How to obtain chemical information

  4. State selected molecular ions • ABC+ (, v, J) • How do we control the internal quantum states? • Excitations can be removed by storage of ABC+ in CRYRING. • This does not always work for J • This does not work for molecules of type A2+ • This does not work if we want to study ABC+ in a known distribution of excited quantum states

  5. Pinhole discharge source • Designed and built at UC Berkely • Characterized at UC Berkeley • Shipped to Stockholm for experiment at CRYRING • Shipped back to Berkeley, redesigned, and characterized • Shipped to Stockholm for new experiment

  6. Discharge Supersonic expansion including ions and neutrals High pressure Vacuum Laser beam for probing

  7. Energy level structure of H3+

  8. Interstellar transitions 2 0 ortho para

  9. Diffuse cloud absorption

  10. Control of vibrational excitation • Electron-impact source • Built and characterized at SRI International in Menlo Park, CA • Shipped AMOLF in Amsterdam and then later to Stockholm

  11. Ground Plate Deflection plates Electron Trap Extraction Plate Repeller plates Hot filament (outside the source) Gas Inlet

  12. V=0,1,2,3! V=0! Ion Source Developments • Better control over vibrational populations • Experiments on SEC and DR • More control over ion source settings • AMOLF & SRI, Phil Cosby • O2+() + Cs  O2*(Ryd,n=3,’= )  O + O + KER(0-3eV, ) • CRYRING • O2+ + e-  (O2*(Ryd) ) O2**  O + O + KER

  13. Biological molecules In the gas phase

  14. Spray needle: The needle is inside a nitrogen- gas filled housing for spray stability. Entrance capillary: The ion droplets are passing through a heated capillary and evaporate.

  15. Exit: After the capillary, the ions are stored and pulsed by a hexapole trap.

  16. Quadrople mass filter Ion trap Electrospray unit with a pulsed hexapole trap experiment Interaction of biomolecular ions with electrons/photons

  17. Beam splitter Image intensifier H CCD- camera O H MCPs and phosphor screen Timing (Camac) PC 16-segmented PMT

  18. Experimental parameters • Data taking rate: 600 - 1000 Hz • Time resolution: 0.6 - 1.0 ns • Energy resolution: 100 meV • No chemical information in the standard set-up

  19. Specifications • Data taking rate > 10 kHz • Time resolution  1 ns • Position resolution  0.1 mm • Dead area 1 cm2 • No chemical information

  20. pump (shg, thg, topas) polychromator CCD sample flow cell probe (wlc) Example: I2Br- + hn I2- + Br  I2Br-/CH3CN +

  21. The Cluster Apparatus

  22. The total cluster machine assembly, combining a laser ablation source with a time-of-flight mass spectrometer Pressure: 10-4 – 10-7 torr inside the machine The extracting electric field: static in Stark spectroscopy switched in lifetime measurements Cold molecules (Ttrans < Trot < Tvibr < Telectr )  only lowest vibrational and electronic states populated

  23. Nd:YAG laser (1064 nm) for ablation of the metal clusters • A tunable ring-dye laser, pumped by an Ar+ laser, for exciting • the molecules. • The narrow bandwidth cw laser light (FWHM ~ 1 MHz) is • pulsed-amplified in a Bethune cell, • pumped by a XeCl excimer laser (308 nm) pulses 10 ns, ~1 J, FWHM < 150 MHz • An ArF excimer laser (193 nm) for ionizing the molecules • Operating frequency: 10 Hz • Auto-scan system. Iodine calibration spectrum.

  24. Conclusions • The ion source R&D is probably too specialized to be of interest for an AlbaNova instrumentation project • The electro-optical part is covered by the KAW application • From the Molecular Physics point of view, detector development is most suited

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