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Holger Kreckel, Andrew Mills, Manori Perera, Brian Siller, Kyle Crabtree, Carrie Kauffman,

High Resolution Spectroscopy of Molecular Ion Beams. Holger Kreckel, Andrew Mills, Manori Perera, Brian Siller, Kyle Crabtree, Carrie Kauffman, Benjamin J. McCall University of Illinois at Urbana-Champaign. SCRIBES. ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC.

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Holger Kreckel, Andrew Mills, Manori Perera, Brian Siller, Kyle Crabtree, Carrie Kauffman,

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  1. High Resolution Spectroscopy of Molecular Ion Beams Holger Kreckel, Andrew Mills, Manori Perera, Brian Siller, Kyle Crabtree, Carrie Kauffman, Benjamin J. McCall University of Illinois at Urbana-Champaign SCRIBES

  2. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Upcoming observatories exploring the molecular universe SOFIA Stratospheric Observatory for Infrared Astronomy Herschel Space Observatory

  3. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Interstellar Medium: density and temperature Molecular clouds: places of stellar birth temperatures: 10-100 K density: 102 - 108 cm-3 • no three-body collisions • no endothermic reactions • no reactions with barriers

  4. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Ions are key! - the UMIST database lists 4572 binary reactions, 2386 ion-neutral reactions, 552 charge exchange reactions, - 2/3 of the reactions are ion-neutral processes, - 30% of these reactions have been measured.

  5. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Sensitive Cooled Resolved Ion BEam Spectroscopy Ion Spectroscopy Techniques Hirota, Amano Oka, Saykally Maier, Nesbitt Supersonic Expansion Velocity Modulation Hollow Cathode SCRIBES     High ion column density     Ion-neutral discrimination       Low rotational temperature        Narrow linewidth    Compatible with cavity-enhanced spectroscopy  ( )  Mass spectrometry of laser-probed ions  Spectral identification of ion mass

  6. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Why Ion Beam Spectroscopy? kinematic compression of the linewidth Δω ~ 1/√ Ebeam

  7. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams SCRIBES setup supersonic expansion source detector 20 cm ion beam cavity mirrors Overlap region particle detector beam modulation plates TOF mass spectrometer laser light

  8. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Ion sources Cold cathode discharge Continuous Supersonic Expansion Cathode 3.5 kV Anode 7.5 kV Extraction plate Ground N2 plasma • new development • requires heavy pumping • rotationally cold • simple • high ion density • rotationally hot

  9. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Continuous supersonic expansion source (K Crabtree, C Kauffman) O-Rings Pinhole Gas flow 3 atm <100 mtorr Anode Macor Spacer Cathode

  10. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Ion optics Goal: optimize ion density in the overlap region ion beam 20 cm ion source Overlap region

  11. Output Input ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Quadrupole vs. asymmetric cylindrical deflector Electrostatic quadrupoles are often used as 90o deflectors +V -V Collimated beam +V -V Diverging beam

  12. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Asymmetric cylindrical deflector R1=140 mm V1=-740 V y x z R2=178 mm V2=+740 V 3 keV ion beam x y y z z z vacuum chamber

  13. xxxxxxxxxx ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Asymmetric cylindrical deflector

  14. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Ion optics Goal: optimize ion density in the overlap region Performance with the cold cathode source: ion beam 20 cm ion source ISource = 30 µA IBeam = 10 µA IOverlap = 2 µA (confined by 4mm apertures,13 cm apart) Overlap region / 30 cm

  15. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Time of Flight Mass Spectrometer (M Perera) Goal: characterize ion beam: composition, energy, energy spread ion beam 20 cm ion source Overlap region beam modulation plates TOF mass spectrometer

  16. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Time of Flight measurements width ~2ns energy spread ~ 2V N+ Beam energy Voltage 3510V TOF 3560V N2+

  17. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams SCRIBES setup Source chamber TOF Mass spectrometer Overlap region

  18. Ti:Sa @ 925 nm Optical Isolator l-meter Etalon Finder FPI AOM Mode Matching Optics ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Spectroscopy: first tests with N2+ cw cavity ringdown spectroscopy (cw-CRDS) detector Source chamber apertures

  19. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Concentration Modulation CRDS • 99.99% RD Mirrors • 33 ms time constant • amin =4x10-9 cm-1 • Concentration Modulation • Beam on/ Beam off • amin =5x10-10 cm-1 • Reduces long term Drift

  20. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams CRDS / representative scans N2+ amin=4.5 x 10-10 cm-1 x10-9 Absorbance (cm-1) Wavelength (nm)

  21. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Next step: velocity modulation (A Mills, B Siller) detector pzt • Use lower finesse cavity • Modulate the velocity of the ion beam by applying field to drift region • Use lock in detection to further reduce noise and increase signal Source chamber apertures PLL

  22. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Cavity enhanced velocity modulation

  23. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Cavity enhanced velocity modulation Siller, B, Mills, A, and McCall B.J., Optics Letters, accepted

  24. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Future: high resolution infrared spectroscopy difference frequency generation laser (DFG) 2.8- 4.8 µm ortho-H3+ para-H3+ Nd:YAG 1064 nm 532 nm pump laser l/4 Ti:Sapph 700 – 990 nm l/2 AOM reference cavity l/2 PPLN detector 2.8 – 4.8 μm

  25. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Future: high resolution infrared spectroscopy Menlo Systems frequency comb Source: NIST Source: Menlo Systems

  26. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Precision Cavity Enhanced Velocity Modulation of N2+ in a AC Discharge Plasma Lock-in-signal 0.001 cm-1 Ferguson 85 MHz CEVMS cm-1

  27. HNN+, HCS+,HOC+, HCO+, CO+,CH+, HCNH+, CH5+, C3H3+, C6H7+ etc, etc .... ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams High resolution Spectroscopy with SCRIBES Almost all the individual parts are working, Now we have to bring them all together! Velocity modulation Expansion source SCRIBES Frequency DFG Laser comb

  28. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Acknowledgements NSF Division of AMO Physics Dreyfus New Faculty Award NASA Laboratory Astrophysics NSF Divisions of Chemistry & Astronomy Packard Fellowship Holger Kreckel, Andrew Mills, Manori Perera, Brian Siller, Kyle Crabtree, Carrie Kauffman, Benjamin J. McCall University of Illinois at Urbana-Champaign Air Force Young Investigator Award Cottrell Scholarship

  29. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams

  30. H3+ detector H3+ (v>1)+ Ar ArH++ H2 + X eV ArH++H2 - 0.57 eV H3+ (v=0)+Ar Ti:Sa Laser ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Action spectroscopy of H3+ in a cryogenic ion trap He, Ar H3+ ArH+ E [cm-1] α [rad] Kreckel et al, JCP 129, 164312 (2008)

  31. ACS San Francisco, Mar 22nd 2010 Holger Kreckel / UIUC High Resolution Spectroscopy of Molecular Ion Beams Sensitive Cooled Resolved Ion BEam Spectroscopy Ion Spectroscopy Techniques Hirota, Amano Oka, Saykally Maier, Nesbitt Supersonic Expansion Velocity Modulation Hollow Cathode SCRIBES     High ion column density     Ion-neutral discrimination       Low rotational temperature        Narrow linewidth    Compatible with cavity-enhanced spectroscopy  ( )  Mass spectrometry of laser-probed ions  Spectral identification of ion mass

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