Spectral Simplification Methods Development Using Waveguide Chirped-Pulse Fourier Transform Microwave Spectroscopy Erin Kent, Steven Shipman New College of Florida June 17, 2014

Shipman Lab NGC 2359 Photo cred: National Geographic, Courtesy of Cerro Tololo Inter-American Observatory in Chile. Cm-wave spectrometer New College of Florida

Very Dense Spectra Problems: Very complex spectra due to line density. Easy to spend hours fitting with no progress. The goal is to speed up analysis.

Spectral Simplification by Temperature Variation By measuring relative transition intensities at different temperatures, lower state energies can be determined. The spectrum must contain one line that has been assigned. Expression from Medvedev, I.R. and De Lucia, F.C., Astrophys. J., 656, (2007). Chose methanol because its spectrum has been thoroughly studied. Its peaks are extremely intense at room temperature.

Lower State Energies a)LSEs from Xu, L.H., and Lovas, F.J., J. Phys. Chem. Ref. Data, 26, (1997). b)LSE relative to , in cm -1 c)LSE from expression, average over five temperature measurements, cm -1

Improvements on Temperature Variation From error analysis, pressure controls were a problem. Use flow cell rather than static cell. A way to improve is to use the temperature varied technique on the mm-wave spectrometer.

Double Resonance Iterations Take spectrum with typical chirped pulse. Find the 100 most intense peaks and build DR pulses. Load each pulse and sweep through the frequency band. Determine level connectivity by intensity modulation. Pump: v = 1, E-state, 5 14 – 5 05 Modulate: v = 1, E-state, 5 23 – methylfuran 10M averages 298 K, 10 mTorr

Results for 2-methylfuran

Future Work Flow cell geometry on the cm-wave spectrometer. Try both techniques on the mm-wave spectrometer. Streamline the double resonance process Incorporate DR into the triples fitter program

Acknowledgments Many thanks to – Lauren Bernier, Ian Finneran, Robert Hincapie, Morgan McCabe, Maria Phillips, Suzanne Setti, Taylor Sweet, and Kenneth Wang – Dr. Steve Shipman Funding from – Office of Naval Research – National Science Foundation – New College of Florida

Centimeter Wave Spectrometer ns sweep (1 – 4.9 GHz) generated by AWG. 2.It is sent into the waveguide and interacts with the molecules. 3.The interaction is detected by the digitizer.

Spectral Simplification by Double Resonance Measurements

Error Analysis Total uncertainty: Data for sample calculation:

Uncertainty contribution from T 1 : Uncertainty contribution from T 2 : Uncertainty contribution from α unas (T 1 ): Uncertainty contribution from α unas (T 2 ): Uncertainty contribution from α as (T 1 ): Uncertainty contribution from α as (T 2 ): Total uncertainty, uncertainty 2 :

Results for 2-ethoxyethanol