Progress In The Development Of An Infrared Ion Beam Spectrometer
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Transcript of Progress In The Development Of An Infrared Ion Beam Spectrometer
Main Title
Kyle Crabtree, Kyle Ford, Holger Kreckel, Andrew Mills, Manori Perera and Ben McCall
University of Illinois at Urbana-Champaign
64th International Symposium on Molecular SpectroscopyOhio State University
June 23th, 2009
Progress In The Development Of An Infrared Ion Beam
Spectrometer
Progress In The Development Of An Infrared Ion Beam
Spectrometer
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OutlineOutline
• Why molecular ion beam
• First generation SCRIBES instrument
• Improvements
• Development of the second generation SCRIBES
• Prospects
SensitiveColdResolvedIonBEamSpectrometer
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Why Use Molecular Ion Beam?
Why Use Molecular Ion Beam?
• Why molecular ions• Astrochemistry• Combustion • Carbocation chemistry• Fundamental insterest
• Why fast ion beam• Kinematic compression
• High resolution spectroscopy• Fingerprint for molecular ions
Andrew Mills, WH02 at 2:05pm
Δω depends on √1/Ufloat voltage
200
150
100
50W
idth
of th
e ab
sorp
tion
lin
e (M
Hz)
10008006004002000
Beam voltage (V)
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First Generation SCRIBES Instrument
First Generation SCRIBES Instrument
Cathode
Anode
Ion Optics
Quadrupoles
Ion Optics
Pulser Plate
Iris
Electron Multiplier
Ringdown Mirrors
InSb
Drift Region
Modeled after Saykally’s instrument (Saykally et al. J. Chem. Phys. 1989, 90 (8), 3893-3894)
• Low ion beam current
• Overlap of the laser
• Modular
• Development of TOF-MS
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Second Generation SCRIBESSecond Generation SCRIBESSource
• High ion beam current• Improved ion optics• Differential pumping
• Modular instrumentation
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Ion Sources Ion Sources
• Cold cathode discharge source
• Considerations for the test application• High ion density• Fast ion beam without a big energy spread• Low maintenance
Precursor gas
Anode Cathode
Fused Silica
• Supersonic source
• Rotationally cold ions
• Continuous source
• Modular
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Uncooled Cold Cathode Source with N2 PlasmaUncooled Cold Cathode Source with N2 Plasma
Source Cathode3.5 kV
Anode7.5 kV
Extraction plateGround
N2 plasma
ISource = 30 µA
IBeam = 10 µA
IOverlap= 1.5 µA
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Ion OpticsIon Optics
Einzel Lens
Side view Frontal view
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Cavity RegionCavity Region
V-V+
Neutrals
Laser path
Ions only3 mm
3 mm
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QuadrupolesQuadrupoles
Output Input
Collimated beam
-V
+V
+V
-V
Diverging beam
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Asymmetrical Deflector Plates
Asymmetrical Deflector Plates
Output parallel beam
Inputfocused beam
(-)V
(+)V
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Mass Selecting RegionMass Selecting Region
• Characterization method• TOF mass spectrometer
Time-of-Flight Mass Spectrometer
• Identity of the masses
• Beam energy
• Beam energy spread
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Collision CellCollision Cell
Laser
Rin
gdow
n T
ime
Con
stan
t (µ
s)
Pseudo-time (s)
CO2 gas at 30 mTorr
Ringdown mirror
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Mass SpectrometerMass Spectrometer
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6
4
2
Inte
nsi
ty (m
V)
353025201510
Mass (amu)
N+
O+
H2O+
N2+
O2+
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Mass Spectrum of N2 PlasmaMass Spectrum of N2 Plasma
Ion beam energy = 3580 V ± 10 V
Power supply output = 3574 V
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6
4
2
0
Inte
nsi
ty (V
)
30252015Mass (amu)
N2+ (m/z=28)90%
N+ (m/z=14)10%
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Growth of SCRIBESGrowth of SCRIBES
1st Generation SCRIBES
cw-Cavity ringdown spectroscopy
2st Generation SCRIBES
Test N2+
Meinel lines
Velocity modulated cavity enhanced spectroscopy
Ion modulated cavity
ringdown spectroscopy
DFG laser
H3+ band
(fundamental)
Supersonic source
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AcknowledgementAcknowledgement
• McCall Group
• Funding
Questions?Questions?