holger kreckel, andrew mills, manori perera, brian siller, kyle crabtree, carrie kauffman, benjamin...
TRANSCRIPT
![Page 1: Holger Kreckel, Andrew Mills, Manori Perera, Brian Siller, Kyle Crabtree, Carrie Kauffman, Benjamin J. McCall University of Illinois at Urbana-Champaign](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e7a5503460f94b7a762/html5/thumbnails/1.jpg)
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
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Herschel Space Observatory
SOFIAStratospheric Observatory for Infrared Astronomy
Upcoming observatories exploring the molecular universe
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
temperatures: 10-100 Kdensity: 102 - 108 cm-3
• no three-body collisions • no endothermic reactions• no reactions with barriers
Molecular clouds:places of stellar birth
Interstellar Medium: density and temperature
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger 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.
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Oka, Saykally Maier, 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
ExpansionSCRIBES
Hollow
Cathode
Hirota, Amano
High ion column density
SensitiveCooledResolvedIonBEamSpectroscopy
Ion SpectroscopyTechniques
)(
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Why Ion Beam Spectroscopy?
kinematic compressionof the linewidth
Δω ~ 1/√ Ebeam
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
SCRIBES setup
Overlap region
TOF mass spectrometer
particledetector
supersonic expansion source
detector
cavitymirrors
laser light
ion beam
beam modulation plates
20 cm
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Ion sources
Cathode3.5 kV
Anode7.5 kV
Extraction plateGround
N2 plasma
Cold cathode discharge
Continuous Supersonic Expansion
• simple• high ion density• rotationally hot
• new development• requires heavy pumping• rotationally cold
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Continuous supersonic expansion source(K Crabtree, C Kauffman)
Gas flow
O-Rings
Pinhole
Anode
Macor SpacerCathode
<100 mtorr
3 atm
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Ion opticsGoal: optimize ion density in the overlap region
Overlap region
ion source
ion beam
20 cm
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Output Input
Collimated beam
-V
+V
+V
-V
Diverging beam
Quadrupole vs. asymmetric cylindrical deflector
Electrostatic quadrupoles are often used as 90o deflectors
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
zy
zy
z
x
z xy
R2=178 mmV2=+740 V
R1=140 mmV1=-740 V
vacuum chamber
3 keV ion beam
Asymmetric cylindrical deflector
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Asymmetric cylindrical deflector
xxxxxxxxxx
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Ion opticsGoal: optimize ion density in the overlap region
Overlap region / 30 cm
ion source
ion beam
20 cm
ISource = 30 µA
IBeam = 10 µA
IOverlap = 2 µA
(confined by 4mm apertures,13 cm apart)
Performance with the cold cathode source:
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger 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
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Time of Flight measurements
N2+
N+
width ~2ns
energyspread ~ 2V
Beam energy
Voltage 3510VTOF 3560V
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
TOF Mass spectrometer
Source chamber
Overlap region
SCRIBES setup
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Source chamber
apertures
Ti:Sa @ 925 nm
Optical Isolator
AOM
Mode Matching
Optics
FPI
-meter
EtalonFinder
detector
Spectroscopy: first tests with N2+
cw cavity ringdown spectroscopy (cw-CRDS)
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger 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
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
924.410924.409924.408924.407924.406924.405
1.0
0.8
0.6
0.4
0.2
20
15
10
5
0
-5
-10
x10-9
min=4.5 x 10-10 cm-1
Wavelength (nm)
Abs
orba
nce
(cm
-1)
x10-9
CRDS / representative scans N2+
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger 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)
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Cavity enhanced velocity modulation
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Cavity enhanced velocity modulation
Siller, B, Mills, A, and McCall B.J., Optics Letters, accepted
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SCRIBES / Spectroscopy with Molecular Ion Beams
Future: high resolution infrared spectroscopydifference frequency generation laser (DFG) 2.8- 4.8 µm
Ti:Sapph700 – 990 nm
532 nmpump laser
reference cavity
/2
Nd:YAG1064 nm
AOM
PPLN
/2/4
detector 2.8 – 4.8 2.8 – 4.8 μμmm
ortho-H3+ para-H3
+
ACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
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SCRIBES / Spectroscopy with Molecular Ion Beams
Source: NIST Source: Menlo Systems
Future: high resolution infrared spectroscopyMenlo Systems frequency comb
ACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
6.6
6.4
6.2
6.0
5.8
5.6
5.4
5.2
10859.3500010859.3450010859.34000
4
3
2
1
0
Q22(14)
CEVMSFerguson 85
MHz
cm-1
0.001 cm-1
Lock
-in-s
igna
lPrecision Cavity Enhanced Velocity
Modulation of N2+ in a AC Discharge Plasma
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger 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 sourceHNN+, HCS+,HOC+,
HCO+, CO+,CH+, HCNH+, CH5
+, C3H3
+, C6H7+
etc, etc ....
Frequencycomb
Velocity modulation
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
NASA LaboratoryAstrophysics
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
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Action spectroscopy of H3+ in a cryogenic ion trap
detector
ArH+H3+
He, Ar
H3+
ArH++H2 - 0.57 eV
H3+ (v=0) +Ar
H3+ (v>1) + Ar
ArH+ + H2 + X eV
E [
cm-1]
Ti:Sa Laser
α [rad]
Kreckel et al, JCP 129, 164312 (2008)
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High Resolution Spectroscopy of Molecular Ion BeamsACS San Francisco, Mar 22nd 2010Holger Kreckel / UIUC
Oka, Saykally Maier, 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
ExpansionSCRIBES
Hollow
Cathode
Hirota, Amano
High ion column density
SensitiveCooledResolvedIonBEamSpectroscopy
Ion SpectroscopyTechniques
)(