JAMES P MCMILLAN CHRISTOPHER F NEESE and FRANK C DE LUCIA The 72 nd International Symposium on Molecular Spectroscopy June 19 2017 ChampaignUrbana Illinois Motivations Primary Understand the complete contribution of each Weed to the Astrophysical data ID: 626888
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Slide1
Dimethyl Ether Between 214.6 and 265.3 GHz: The Complete, Temperature Resolved Spectrum
JAMES P. MCMILLAN, CHRISTOPHER F. NEESE, and FRANK C. DE LUCIAThe 72nd International Symposium on Molecular Spectroscopy June 19, 2017Champaign-Urbana, IllinoisSlide2
Motivations
Primary: Understand the complete contribution of each ‘Weed’ to the Astrophysical data Bonus: Obtaining Dipole Moments and Lower State Energies which may aide in QM assignments
Methodology
: Temperature Dependent Approach to Spectroscopy
ALMA Science Verification Data
Fortman et al.
J.Mol.Spectrosc
280:11-20
(2012)Slide3
Processing Steps
The Complete, Experimental ApproachDecontaminationPoint by Point Output EvaluationMaking a Line ListSlide4
Processing Steps
The Complete, Experimental ApproachDecontaminationPoint by Point Output EvaluationMaking a Line ListSlide5
Acquiring the Intensity Calibrated
Complete Experimental Spectrum (CES)
~1 K per scan
Local Thermodynamic Equilibrium
: Contamination
: Acquire
CES
: Pressure vs. Doppler Broadening
Steps:
10 Heaters
Sample
Transmitter
THz Source
Detector
6 meters
Butterfly ValveSlide6
The Point-by-point Technique
A(
)
K =
= W
Doppler width:
More constants:
Doppler Broadened Naperian Absorbance:
A(
)
Slide7
The Point-by-point Technique
K =
= W
Doppler width:
More constants:
A(
)
Calibrate T and
nL
/Q
Generate
and
Input
Output
Fit a single scan; multiple lines
Fit a single frequency bin; all scans
Slide8
The Point-by-point Technique
1.) Simply Download the table of
and
.
2.)Choose your temp and plot!
A(
)
Incomplete Methyl Formate Predictions
K =
= W
Doppler width:
More constants:
McMillan et al.
ApJ
823
:1 (2016)Slide9
Processing Steps
The Complete, Experimental ApproachDecontaminationPoint by Point Output EvaluationMaking a Line ListSlide10
Decontamination
‘Wheel-O-Contamination’
Untapped 210-270 data
MeCN
,
VCN
,
EtCN found in Dimethyl Ether
EtCN, VCN already published in 210 bandMeCN work product available to OSUSlide11
Decontamination
Find reference contaminant linesCalculate contaminant concentration for each scanSimulate contaminant signal and subtract from Dimethyl Ether signalSlide12
Decontamination
Successful Contaminant Removal:
Methyl Formate
Blends handled well
Peak intensities consistent with catalog predictions
Uncontaminated regions left unaffected
McMillan et al.
ApJ
823:1 (2016)Slide13
Decontamination
Successful Contaminant Removal:
Dimethyl Ether
MeCN
strongest contaminant at ~3%
EtCN
& VCN were 2nd order contaminants (0.1% of analyte)
Easier than:
MeOH
ApJ 795 56 (2014)
Methyl Formate
ApJ
823
:1 (2016)Slide14
Processing Steps
The Complete, Experimental ApproachDecontaminationPoint by Point Output EvaluationMaking a Line ListSlide15
Point by Point Output Evaluation
Error in Energy for
117
Strongest Lines at 300K
Error calculated against CDMS Catalog
RMS Error ~ 13.24 cm
-1
Consistent with previous point by point studies
Energies found by fitting:Slide16
Point by Point Output Evaluation
- CDMSCount of Lines Sorted by Intensity
-
Experiment
CDMS Catalog includes
only
the ground state
Thousands of new lines, many with nontrivial intensity.Boltzmann Factor for the first uncatalogued stateSlide17
Processing Steps
The Complete, Experimental ApproachDecontaminationPoint by Point Output EvaluationMaking a Line ListSlide18
OSU Line List vs CES
Errors in making the line list
OSU Line List is derived from OSU CES
Blends prove problematic
~1% of the 6000 + lines are affected
OSU CES reproduces experimental data well, even degenerate blendsSlide19
OSU Line List vs CES
OSU Line List is derived from OSU CES
Blends prove problematic
~1% of the 6000 + lines are affected
OSU CES reproduces experimental data well, even degenerate blends
Errors in making the line listSlide20
OSU Line List vs CES
OSU Line List is derived from OSU CES
Blends prove problematic
~1% of the 6000 + lines are affected
OSU CES reproduces experimental data well, even degenerate blends
Errors in making the line listSlide21
Summary
Complete ‘Point by Point’ Spectra has been producedThousands of new lines, many with nontrivial intensity.OSU Line Lists require minor corrections or separate analysisThanks to NASA and the NSF for funding this project.