SCRIBES Sensitive Cooled Resolved Ion BEam Spectroscopy Holger
SCRIBES Sensitive Cooled Resolved Ion BEam Spectroscopy Holger Kreckel, Andrew Mills, Manori Perera, Brian Siller, Kyle Crabtree, Carrie Kauffman, Benjamin J. Mc. Call University of Illinois at Urbana-Champaign SCRIBES
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Interstellar Medium: density and temperature Molecular clouds: places of stellar birth temperatures: density: 10 -100 K 102 - 108 cm-3 • no three-body collisions • no endothermic reactions • no reactions with barriers
Midwest Astronomy Meeting, Nov 7 th 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
Midwest Astronomy Meeting, Nov 7 th 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.
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Ion Spectroscopy Techniques Hirota, Amano Maier, Nesbitt Velocity Modulation Hollow Cathode Supersonic Expansion Oka, Saykally 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 Sensitive Cooled Resolved Ion BEam Spectroscopy SCRIBES
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Why Ion Beam Spectroscopy? kinematic compression of the linewidth Δω ~ 1/√ Ebeam
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams SCRIBES setup detector supersonic expansion source 20 cm ion beam cavity mirrors Overlap region beam modulation plates TOF mass spectrometer laser light particle detector
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Ion sources Cold cathode discharge Cathode 3. 5 k. V Extraction plate Ground Continuous Supersonic Expansion Anode 7. 5 k. V N 2 plasma • simple • high ion density • rotationally hot • new development • requires heavy pumping • rotationally cold
Midwest Astronomy Meeting, Nov 7 th 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 Cathode Macor Spacer
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Ion optics Goal: optimize ion density in the overlap region beam 20 cm ion source Overlap region
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Quadrupole vs. asymmetric cylindrical deflector Electrostatic quadrupoles are often used as 90 o deflectors -V +V Collimated beam +V -V Diverging beam Output Input
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Asymmetric cylindrical deflector R 1=140 mm V 1=-740 V z y x R 2=178 mm V 2=+740 V y x y z z z 3 ke. V ion beam vacuum chamber
Midwest Astronomy Meeting, Nov 7 th 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 Overlap region / 30 cm ISource = 30 µA IBeam = 10 µA IOverlap = 2 µA (confined by 4 mm apertures, 13 cm apart)
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Time of Flight Mass Spectrometer (M Perera) Goal: characterize ion beam: composition, energy spread ion beam 20 cm ion source Overlap region beam modulation plates TOF mass spectrometer
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Time of Flight measurements N+ Beam energy width ~2 ns Voltage TOF energy spread ~ 2 V N 2 + 3510 V 3560 V
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams SCRIBES setup Source chamber TOF Mass spectrometer Overlap region
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Spectroscopy: first tests with N 2+ cw cavity ringdown spectroscopy (cw-CRDS) detector 1 st bender Ti: Sa @ 925 nm Source chamber Optical Isolator l-meter Etalon Finder FPI AOM apertures 2 nd bender Mode Matching Optics
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Concentration Modulation CRDS • 99. 99% RD Mirrors 33 ms time constant amin =4 x 10 -9 cm-1 • Concentration Modulation Beam on/ Beam off amin =5 x 10 -10 cm-1 Reduces long term Drift
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams CRDS / representative scans N 2+ Absorbance (cm-1) x 10 -9 amin=4. 5 x 10 -10 cm-1 Wavelength (nm)
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Next step: velocity modulation (A Mills, B Siller) detector pzt 1 st bender PLL 2 nd bender Source chamber • Use lower finesse cavity • Modulate the velocity of the ion beam by applying field to drift region apertures • Use lock in detection to further reduce noise and increase signal
Midwest Astronomy Meeting, Nov 7 th 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-H 3+ para-H 3+ Nd: YAG 1064 nm l/4 l/2 AOM 532 nm pump laser Ti: Sapph 700 – 990 nm reference cavity PPLN detector 2. 8 – 4. 8 μm l/2
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Future: high resolution infrared spectroscopy Menlo Systems frequency comb Source: NIST Source: Menlo Systems
Midwest Astronomy Meeting, Nov 7 th 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+, CH+, HCNH+, CH 5+, C 3 H 3 + , C 6 H 7 + etc, etc. . Expansion source SCRIBES DFG Laser Frequency comb
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Acknowledgements NSF Division of AMO Physics Dreyfus New Faculty Award NASA Laboratory Astrophysics NSF Divisions of Chemistry & Astronomy Holger Kreckel, Andrew Mills, Manori Perera, Brian Siller, Kyle Crabtree, Carrie Kauffman, Benjamin J. Mc. Call University of Illinois at Urbana-Champaign Packard Fellowship Air Force Young Investigator Award Cottrell Scholarship
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams N+ width ~2 ns energy spread ~ 2 V N 2 +
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams width ~2 ns energy spread ~ 2 V
Midwest Astronomy Meeting, Nov 7 th 2009 Holger Kreckel / UIUC SCRIBES / Spectroscopy with Molecular Ion Beams Molecules in Interstellar Space! currently ~150 molecules detected by Spectroscopy
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