the complete, temperature resolved spectrum of methyl formate between 214 and 265 ghz james p....
DESCRIPTION
Point by Point Temperature ramp, acquire 100s of spectra ~10 6 frequency bins Calibrate Temperature and Number Density for each scan Fit each frequency bin to the hundreds of scansTRANSCRIPT
The Complete, Temperature Resolved Spectrum Of Methyl Formate Between
214 and 265 GHz
JAMES P. MCMILLAN, SARAH M. FORTMAN, CHRISTOPHER F. NEESE, and FRANK C. DE LUCIA
The 70th International Symposium on Molecular Spectroscopy June 25, 2013
The Ohio State University
MotivationsPrimary: 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
“An Analysis of a Preliminary ALMA Orion KL Spectrum via the use of Complete Experimental Spectra from the Laboratory” Fortman S. M., McMillan J.P., Neese C.F., Randall S., Remijan A.J., Wilson T.L., De Lucia F.C., J.Mol.Spectrosc 280:11-20
Point by Point
• Temperature ramp, acquire 100s of spectra~106 frequency bins
• Calibrate Temperature and Number Density for each scan
• Fit each frequency bin to the hundreds of scans
Point by Point
K = = W
Doppler width: More constants:
A()
Calibrate T and nL/Q
Generate and
InputOutput
Fit a single scan; multiple lines
Fit a single frequency bin; all scans
~𝐸 𝑙=𝐸𝑙+𝑘ln (2 )𝑊 2 ¿
Processing Steps
• Temperature Calibration
• Decontamination
• Point by Point Output Evaluation
Temperature Calibration
Preliminary Temperatures
Additional catalogs found from JPL reference pdf:
Ilyushin et al. J. Mol. Spectrosc. 255 32-38Oesterling et al. ApJ. 521 255-260.Carvajal et al. J. Mol. Spectrosc. 246 158-166
Using both vibrational states out performs using just the ground state or the 1st excited
Temperature Calibration
Trends in Ka
Tadpole Pattern
Better fit with both vibrational states
Temperature Calibration
Trends in Ka
Tadpole Pattern
Better fit with both vibrational states
Temperature Calibration
Trends in Ka
Tadpole Pattern
Better fit with both vibrational states
Temperature Calibration
Temperatures Calculated by Reference Lines
425 Spectral Scans
248-408 K over 287 minutes
346 Reference Lines
JPL Catalog was used
Temperature Calibration
Trends in Ka
Tadpole Pattern
Better fit with both vibrational states
Suggests a problems with catalog intensity
Temperature Fit Residuals from Point by Point
Processing Steps
• Temperature Calibration
• Decontamination
• Point by Point Output Evaluation
Decontamination
‘Wheel-O-Contamination’
Untapped 210-270 data
MeOH and EtCN found in Methyl Formate
MeOH, EtCN, VCN already published in 210 band
Decontamination
• Find reference contaminant lines
• Calculate contaminant concentration for each scan
• Simulate contaminant signal and subtract from Methyl Formate signal
DecontaminationExamples of Successful Contaminant Removal
Blends handled well
Peak intensities consistent with catalog predictions
Uncontaminated regions left unaffected
Processing Steps
• Temperature Calibration
• Decontamination
• Point by Point Output Evaluation
Point by Point Output Evaluation
~𝐸 𝑙=𝐸𝑙+𝑘ln (2 )𝑊 2 ¿
Error in Energy for 408 Strongest Lines at 300K
Error calculated against JPL Catalog
Two red points were blended with uncatalogued lines
RMS Error ~ 13.75 cm-1
Energies found by fitting:
Point by Point Output Evaluation
- JPL
Count of Lines Sorted by Intensity
- Experiment
JPL Catalog includes only the ground and 1st excited vibrational states
Thousands of new lines, many with nontrivial intensity.
Boltzmann Factor for the first uncatalogued state
Summary
• Complete ‘Point by Point’ Spectra has been produced
• Systematic Trends in Temperature Fit Residuals– Potential Intensity issues in the catalogues
• Thousands of new lines, many with nontrivial intensity.
• Thanks to NASA and the NSF for funding this project.