SCRIBES Sensitive Cooled Resolved Ion BEam Spectroscopy Holger Kreckel, Andrew Mills, Manori Perera, Brian Siller, Kyle Crabtree, Carrie Kauffman, Benjamin J. McCall University of Illinois at Urbana-Champaign SCRIBES

Interstellar Medium: density and temperature Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with 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

Molecules in Interstellar Space? Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Molecules in Interstellar Space? “It is difficult to admit the existence of molecules in interstellar space because when once a molecule becomes dissociated there seems no chance of the atoms joining up again.” Sir Arthur Stanley Eddington (1926) yet ... more than 150 interstellar molecules detected ... and counting

- the UMIST database lists 4572 binary reactions, Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with 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.

                           Ion Spectroscopy Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Sensitive Cooled Resolved Ion BEam Spectroscopy Ion Spectroscopy Techniques Oka, Saykally Hirota, Amano Maier, Nesbitt Velocity Modulation Hollow Cathode Supersonic Expansion 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

kinematic compression Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Why Ion Beam Spectroscopy? kinematic compression of the linewidth Δω ~ 1/√ Ebeam

SCRIBES setup SCRIBES / Spectroscopy with Molecular Ion Beams Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with 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

Ion sources Cold cathode discharge Continuous Supersonic Expansion Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with 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

Continuous supersonic expansion source (K Crabtree, C Kauffman) Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Continuous supersonic expansion source (K Crabtree, C Kauffman) O-Rings 3 atm Pinhole Gas flow ~300 mtorr Anode Macor Spacer Cathode

Goal: optimize ion density in the overlap region Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Ion optics Goal: optimize ion density in the overlap region Overlap region ion source ion beam 20 cm

Quadrupole vs. asymmetric cylindrical deflector Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Quadrupole vs. asymmetric cylindrical deflector Electrostatic quadrupoles are often used as 90o deflectors Output Input +V -V Collimated beam +V -V Diverging beam

Asymmetric cylindrical deflector Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Asymmetric cylindrical deflector z x y R2=178 mm V2=+740 V R1=140 mm V1=-740 V vacuum chamber 3 keV ion beam z y

Goal: optimize ion density in the overlap region Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with 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

Time of Flight Mass Spectrometer Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams 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

Time of Flight measurements Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Time of Flight measurements N+ width ~2ns energy spread ~ 2V Beam energy Voltage 3510V TOF 3560V N2+

SCRIBES setup SCRIBES / Spectroscopy with Molecular Ion Beams Source Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams SCRIBES setup TOF Mass spectrometer Source chamber Overlap region

Spectroscopy: first tests with N2+ Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Spectroscopy: first tests with N2+ cw cavity ringdown spectroscopy (cw-CRDS) Source chamber 1st bender 2nd bender apertures Ti:Sa @ 925 nm Optical Isolator AOM Mode Matching Optics FPI l-meter Etalon Finder detector

Concentration Modulation CRDS Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with 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

CRDS / representative scans N2+ Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams CRDS / representative scans N2+ amin=4.5 x 10-10 cm-1 x10-9 Absorbance (cm-1) Wavelength (nm)

Next step: velocity modulation Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with 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 1st bender PLL apertures 2nd bender

Future: high resolution infrared spectroscopy Midwest Astronomy Meeting, Nov 7th 2009 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

Future: high resolution infrared spectroscopy Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Future: high resolution infrared spectroscopy Menlo Systems frequency comb Source: NIST Source: Menlo Systems

High resolution Spectroscopy with SCRIBES Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams High resolution Spectroscopy with SCRIBES Almost all the individual parts are working, Now we have to bring them all together! HNN+, HCS+,HOC+, HCO+, CO+,CH+, HCNH+, CH5+, C3H3+, C6H7+ etc, etc .... Expansion source SCRIBES Frequency DFG Laser comb

Acknowledgements NSF Division of AMO Physics Dreyfus New Faculty Award Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Acknowledgements 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

SCRIBES / Spectroscopy with Molecular Ion Beams Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams

SCRIBES / Spectroscopy with Molecular Ion Beams Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams

N+ width ~2ns energy spread ~ 2V N2+ Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams N+ width ~2ns energy spread ~ 2V N2+

width ~2ns energy spread ~ 2V Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams width ~2ns energy spread ~ 2V

Molecules in Interstellar Space! Midwest Astronomy Meeting, Nov 7th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Molecules in Interstellar Space! currently ~150 molecules detected by Spectroscopy