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

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

3. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC temperatures: 10-100 K density: 10 2 - 10 8 cm -3 no three-body collisions no endothermic reactions no reactions with barriers Molecular clouds: places of stellar birth Interstellar Medium: density and temperature

4. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC 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. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC Oka, SaykallyMaier, Nesbitt    Ion-neutral discrimination Low rotational temperature Narrow linewidth Compatible with cavity-enhanced spectroscopy Mass spectrometry of laser-probed ions Spectral identification of ion mass Velocity Modulation Supersonic Expansion SCRIBES  Hollow Cathode Hirota, Amano  High ion column density  S ensitive C ooled R esolved I on BE am S pectroscopy  Ion Spectroscopy Techniques ) (

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

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

8. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC Ion sources Cathode 3.5 kV Anode 7.5 kV Extraction plate Ground N 2 plasma Cold cathode discharge Continuous Supersonic Expansion simple high ion density rotationally hot new development requires heavy pumping rotationally cold

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

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

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

12. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC z y z y z x z x y R 2 =178 mm V 2 =+740 V R 1 =140 mm V 1 =-740 V vacuum chamber 3 keV ion beam Asymmetric cylindrical deflector

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

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

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

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

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

18. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC Source chamber apertures Ti:Sa @ 925 nm Optical Isolator AOM Mode Matching Optics FPI -meter Etalon Finder detector Spectroscopy: first tests with N 2 + cw cavity ringdown spectroscopy (cw-CRDS)

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

20. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC  min =4.5 x 10 -10 cm -1 Wavelength (nm) Absorbance (cm -1 ) x10 -9 CRDS / representative scans N 2 +

21. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC Source chamber apertures 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 PLL pzt detector Next step: velocity modulation (A Mills, B Siller)

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

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

24. SCRIBES / Spectroscopy with Molecular Ion Beams Future: high resolution infrared spectroscopy difference frequency generation laser (DFG) 2.8- 4.8 µm Ti:Sapph 700 – 990 nm 532 nm pump laser reference cavity /2 Nd:YAG 1064 nm AOM PPLN /2 /4 detector 2.8 – 4.8 μm ortho-H 3 + para-H 3 + ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC

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

26. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC CEVMS Ferguson 85 MHz cm -1 0.001 cm -1 Lock-in-signal Precision Cavity Enhanced Velocity Modulation of N 2 + in a AC Discharge Plasma

27. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC SCRIBES High resolution Spectroscopy with SCRIBES Almost all the individual parts are working, Now we have to bring them all together! DFG Laser Expansion source HNN +, HCS +,HOC +, HCO +, CO +,CH +, HCNH +, CH 5 +, C 3 H 3 +, C 6 H 7 + etc, etc.... Frequency comb Velocity modulation

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

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

30. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC Action spectroscopy of H 3 + in a cryogenic ion trap detector ArH + H3+H3+ He, Ar H3+H3+ ArH + +H 2 - 0.57 eV H 3 + (v=0) +Ar H 3 + (v>1) + Ar ArH + + H 2 + X eV E [cm -1 ] Ti:Sa Laser α [rad] Kreckel et al, JCP 129, 164312 (2008)

31. High Resolution Spectroscopy of Molecular Ion Beams ACS San Francisco, Mar 22 nd 2010 Holger Kreckel / UIUC Oka, SaykallyMaier, Nesbitt    Ion-neutral discrimination Low rotational temperature Narrow linewidth Compatible with cavity-enhanced spectroscopy Mass spectrometry of laser-probed ions Spectral identification of ion mass Velocity Modulation Supersonic Expansion SCRIBES  Hollow Cathode Hirota, Amano  High ion column density  S ensitive C ooled R esolved I on BE am S pectroscopy  Ion Spectroscopy Techniques ) (