HIGH RESOLUTION JET COOLED CAVITY RINGDOWN SPECTROSCOPY OF THE A STATE BAND OF THE NO 3 RADICAL Terrance J. Codd, Mourad Roudjane and Terry A. Miller The Ohio State University ~

Introduction Having observed and assigned the 3 fundamental using moderate resolution radiation we would like to obtain a high resolution spectrum of this band to confirm the assignment Also, see if the rotational structure indicates the presence of strong JT coupling In the limit of strong JT coupling the molecule would be permanently distorted to a lower symmetry geometry Rotational structure is the best way to observe distortions of molecular geometry

HR JC-CRDS CW Ti:Sa YAG 20 Hz YVO 4 Ring D 2 Herriott Type Multipass Cell 1st stokes ∼ 1.1 μm ∼ 2 mJ ~9.5 atm ~210 MHz FWHM InGaAs Detector 67 cm WLM ~7 – 30 MHz FWHM (FT limited) 30 – 100 mJ/pulse

IR Beam 9 mm -HV radical densities of molecules/cm 3 (10 mm downstream, probed) rotational temperature of K plasma voltage ~ 700 V, I  1 A (~ 400 mA typical), 100 µs length dc discharge, discharge localized between electrode plates, increased signal compared to longitudinal geometry Previous similar slit-jet designs: D.J. Nesbitt group, Chem. Phys. Lett. 258, 207 (1996); R.J. Saykally group, Rev. Sci. Instrum. 67, 410 (1996); T. A. Miller group, Phys. Chem. Chem. Phys. 8, 1682 (2006). 5 cm 5 mm 10 mm Electrode Viton Poppet Precursor in Buffer Gas Slit Jet/Discharge

Calibration Spectrum is calibrated at each frequency point using a High Finesse WS-7 wavemeter This has a 3  accuracy of 60MHz and a precision of 20 MHz We compared calibration using the wavemeter to calibration using waterlines and found they differed by 100 MHz We experimentally measured the D 2 Raman shift to be cm -1 at our conditions

Moderate Resolution Spectrum Move to 8750 cm -1 to scan relatively weak parallel band there to confirm the assignment ppm/pass

Spectrum Shown is the spectrum of the band ~160 lines are resolved ppm/pass

Comparison: v ppm/pass data: Ming-Wei Chen Dissertation, 2011

Comparison: v ppm/pass data: Ming-Wei Chen Dissertation, 2011

Model Used for Simulation We used our SPECVIEW software with an oblate symmetric top model with spin-rotation, centrifugal distortion, and NSSW We used Hirota’s ground state constants and left them fixed through all fits 1 Fits are performed by iteratively assigning peaks and running a least squares regression of free parameters and then assigning more peaks A total of 104 lines were used in the final step of the fit 1. Hirota, E. Ishiwata, T. Kawaguchi, K. Fujitake, M. Ohashi, N. Tanaka, I. J. Chem. Phys. 107, 2829 (1997)

Simulation vs. Experiment Simulation at 17 K 104 lines are assigned Standard Deviation of fit is 158 MHz Fixed ground state constants to Hirota’s 1 Excited StateUncertainty C E-05 B E-05 DkDk E E-06 D jk E E-06 DjDj E E-07 Ebb E-04 Te E-03 Exp Sim 1. Hirota, E. Ishiwata, T. Kawaguchi, K. Fujitake, M. Ohashi, N. Tanaka, I. J. Chem. Phys. 107, 2829 (1997)

Simulation vs. Experiment Simulation is very good For some transitions 1 line is predicted but 2 are observed Where a ‘split’ line is in one branch, corresponding peaks can be seen in the other two Ground state combination differences confirm that these belong to the same excited state level ppm/pass

Split Peak Analysis Split PeaksFrequencyWeighted PositionPredicted PositionWeight-Pred Fit Std Dev in MHzRMS Error in MHz Integrated ‘split’ peaks to find weighted position and compared it to the predicted position from the simulation.

Split Lines Shown are some of the K = 3 levels and their splitting. J’ N’ K’ Energy levels (cm-1) Diff (cm-1)Diff(MHz) 9/ / / / / / / / / /

Conclusions We have obtained a high resolution spectrum of the previously unassigned band of the A state of NO 3 We have analyzed this spectrum using an oblate symmetric top model The rotational structure does not indicate the presence of strong JT coupling Several excited state rotational levels are split. This could be caused by perturbations from dark vibronic levels ~

Acknowledgements Terry Miller Miller Group Neal Kline Rabi Chhantyal-Pun Mourad Roudjane Takashige Fujiwara Dianping Sun Ming-Wei Chen  NSF - $$$ You for your attention!  Currently at University of Illinois Urbana-Champaign

Hirota A-State (4 1 0 )Uncertainty X-StateUncertainty B E-05B E-05 C E-07C *** DNDN 1.433E-062.3E-08DNDN E-08 D NK E-08D NK E-07 DKDK ***DKDK *** E bb E-04E bb E-04 Te Te0 Ming-Wei Chen A-State (4 1 0 )Uncertainty B E-05 C E-05 DNDN -2.54E-062.4E-07 E bb E-04 Te E-03 Constants Preliminary Fit Excited StateUncertainty C E-05 B E-05 DKDK E E-06 D NK E E-06 DNDN E E-07 E bb E-04 Te E-03 Hirota, E. Ishiwata, T. Kawaguchi, K. Fujitake, M. Ohashi, N. Tanaka, I. J. Chem. Phys. 107, 2829 (1997)