High-Resolution Spectroscopy of the ν16 Band of 1,3,5-Trioxane
Bradley M. Gibson and Nicole KoeppenDepartment of Chemistry, University of Illinois at Urbana-ChampaignBenjamin J. McCall Departments of Chemistry and Astronomy, University of Illinois at Urbana-Champaign
Outline
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1. Motivations2. Previous Work3. Spectrometer Design
a) CRDS Overviewb) Optical Layout
4. Observed Spectra5. Future Work
Figure from: M. Kobayashi et al., “Vibrational Spectra of Trioxane and Trioxane-d6” J. Chem. Phys. 44, 922 (1966)
Why study trioxane?
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• C3v symmetry, chair conformation• Only one rotationally-resolved band
observed• 220 km/mol band at 1178 cm-1
• Strong band would be useful for characterizing newlydeveloped equipment
Figure from: J-F. Henninot et al., “The Infrared Spectrum of Trioxane in a Supersonic Slit Jet”. J. Mol. Spect. 152, 62 (1992)
Previous Studies
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• Numerous low-res vibrational spectra, including Kobayashi et al. in 1965
• Microwave spectrum observed by Oka et al. in 1963• Only one rotationally-resolved spectrum, ν17 by Henninot et al.
in 1992
How does CRDS work?
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AOMLaser PiezoPo
wer
Time
How does CRDS work?
{6}
AOMLaser PiezoPo
wer
Time
How does CRDS work?
{7}
AOMLaser PiezoPo
wer
Time
Cavity on-resonance
How does CRDS work?
{8}
AOMLaser PiezoPo
wer
Time
AOM switched off
How does CRDS work?
{9}
AOMLaser Piezo
Pow
er
Time
• Cavity enhanced sensitivity• No noise from laser power
fluctuation
Spectrometer Layout
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EC-QCL
Fresnel Rhomb
Wavemeter
SO2 Cell
PolarizerCavity
AOM
Figure generated using PGopher
What do we expect to see?
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1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184Wavenumber/cm-1
0.0
0.5
1.0
1.5
2.0
2.5
Nor
mal
ized
Inte
nsity
/ cm
-1
What did we see?
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500
450
400
350
Loss
-Per
-Pas
s (p
pm)
1186118411821180117811761174
Frequency (cm-1
)
What did we see?
{13}
430
420
410
400
390
380
370
360
Loss
-Per
-Pas
s (p
pm)
1180.21180.01179.81179.6
Frequency (cm-1
)
Are the spectra reproducible?
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500
450
400
350
300
Loss
-Per
-Pas
s (p
pm)
1179.21179.01178.81178.6
Frequency (cm-1
)
Peak positions vary by approximately ±150 MHz
What’s causing the uncertainty?
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1180.040
1180.035
1180.030
1180.025Freq
uenc
y (c
m-1
)
5004003002001000
Time (s)
~131 MHz St.Dev.
Figure generated using PGopher
What resolution do we need?
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1178.0 1178.2 1178.4 1178.6 1178.8 1179.0 1179.2 1179.4 1179.6 1179.8 1180.0Wavenumber/cm-1
0.1
0.2
0.3
0.4
0.5
0.6
Nor
mal
ized
Inte
nsity
/ cm
-1
Simulation convolved with 150 MHz gaussian
Figure generated using PGopher
What resolution do we need?
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1178.0 1178.2 1178.4 1178.6 1178.8 1179.0 1179.2 1179.4 1179.6 1179.8 1180.0Wavenumber/cm-1
0
1
2
3
Nor
mal
ized
Inte
nsity
/ cm
-1
Simulated with 30 MHz resolution – resolved!
Is our locked EC-QCL sufficient?
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392
390
388
386
384
382Loss
-Per
-Pas
s (p
pm)
50403020100
Relative Frequency (MHz)
Feature <10 MHz (approx) resolved!
Wikimedia CommonsFigures from: B.M. Gibson et al., “Development of a Sheath-Flow Supercritical Fluid Source for Vaporization of Nonvolatiles
at Moderate Temperatures”. 68th ISMS, 2013
What’s next?
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• Finish stabilizing EC-QCL• Re-acquire spectrum with better stability• Fit spectrum
• New experiments:• Cyanuric Acid• Supercritical Fluid Source
Acknowledgements
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