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The Performance Of A Continuous Supersonic Expansion Discharge Source

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The Performance Of A Continuous Supersonic Expansion Discharge Source Carrie A. Kauffman, Kyle N. Crabtree, Benjamin J. McCall Department of Chemistry, University of ... – PowerPoint PPT presentation

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Title: The Performance Of A Continuous Supersonic Expansion Discharge Source


1
The Performance Of A Continuous Supersonic
Expansion Discharge Source
  • Carrie A. Kauffman, Kyle N. Crabtree, Benjamin J.
    McCall
  • Department of Chemistry, University of Illinois
  • June 24th, 2010

2
Outline
3
Motivation
4
Motivation
Interstellar medium Diffuse Molecular
Clouds Temp 60 K Density 101103 cm-3 Dense
Molecular Clouds Temp 20 K Density 104106
cm-3
5
Sensitive Cooled Resolved Ion BEam Spectroscopy
For more on SCRIBES, please stay for RE06.
6
Production of Cold Molecular Ions
Trot 300 K
Trot 110-180 K
7
Production of Cold Molecular Ions
Trot 110 K
-No spectral intensity dilution, reduced spectral
congestion -gt easy spectral assignment -Astrophyis
cally relevant temperatures-gt molecular
fingerprint for astronomers
8
Continuous Supersonic Expansion Discharge Source
Small Orifice
Trot 5-30 K
High Pressure Gas
Low Pressure
9
Continuous Supersonic Expansion Discharge Source
Leybold 3-Stage Pumping System Pumping speed
3600 L/s
10
Basic Design
Gas Input
High Temp Silicone O-rings
Cathode
Macor Cap
Anode
Macor Spacer
11
H3
Rotational Constant 43.56 cm-3
McCall, B.J. Ph.D. Thesis, University of Chicago,
2001.
12
Experimental Set-up
13
Source Conditions
  • 2-3 bar of backing pressure
  • Orifice Size flared like a trumpet 0.5 to 4.1 mm
    in diameter
  • Typical Chamber Pressure 200-300 mTorr
  • Negative voltage applied to cathode and anode
    held at ground
  • Current 10-130 mA

14
Sample Spectra
15
Results
Low Current Regime
  • ? column density with increasing discharge
    current.
  • ? in rotational temperature with increasing
    discharge current.
  • Operated for over 150 hours without source
    failure.

16
Results
High Current Regime
  • ? column density
  • No change in rotational temperature
  • 50 hours of operation

17
Comparison
This Work Xu et al.1 Tom et al.2 Davis et al.3
Type of Source Continuous nozzle Continuous slit-jet corona Pulse Nozzle Pulsed Slit
Rotational Temperature (K) 50-110 77 60-100 Not Reported
Ion Density (cm-3) 8 1010 to 2 1012 Not Reported 1 x 1011 5x1010
3. Davis et al. Chem. Phys. Lett. 2001, 344,
23-30.
1. Xu et al. Chem. Phys. Lett. 1995, 242 126-131.
2. Tom et al. J. Chem. Phys. 2010, 132, 081103.
18
Summary
  • Rotational temperatures in the range of 50-110
    Kelvin.
  • Robust durable design capable of operating for
    an extended period of time.
  • Ion densities comparable to pulsed sources?
    Increased sensitivity!
  • Plans for improving this design will be tested by
    studying the ?1 fundamental band of HN2.

19
Acknowledgments
For more information visit the McCall Research
Group at http//bjm.scs.uiuc.edu
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