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HIGH RESOLUTION JET COOLED CAVITY RINGDOWN SPECTROSCOPY OF THE A STATE 3 1 0 BAND OF THE NO 3 RADICAL Terrance J. Codd, Mourad Roudjane and Terry A. Miller.

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Presentation on theme: "HIGH RESOLUTION JET COOLED CAVITY RINGDOWN SPECTROSCOPY OF THE A STATE 3 1 0 BAND OF THE NO 3 RADICAL Terrance J. Codd, Mourad Roudjane and Terry A. Miller."— Presentation transcript:

1 HIGH RESOLUTION JET COOLED CAVITY RINGDOWN SPECTROSCOPY OF THE A STATE 3 1 0 BAND OF THE NO 3 RADICAL Terrance J. Codd, Mourad Roudjane and Terry A. Miller The Ohio State University ~

2 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

3 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

4 IR Beam 9 mm -HV radical densities of 10 12 - 10 13 molecules/cm 3 (10 mm downstream, probed) rotational temperature of 15 - 30 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

5 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 2987.277 cm -1 at our conditions

6 Moderate Resolution Spectrum Move to 8750 cm -1 to scan relatively weak parallel band there to confirm the assignment ppm/pass 430430 110420110420 310310 210420210420 220410220410 120420120420 230230 210430210430 120410120410

7 Spectrum Shown is the spectrum of the 3 1 0 band ~160 lines are resolved ppm/pass

8 Comparison: 3 1 0 v 4 1 0 310310 410410 ppm/pass 4 1 0 data: Ming-Wei Chen Dissertation, 2011

9 Comparison: 3 1 0 v 4 1 0 310310 410410 ppm/pass 4 1 0 data: Ming-Wei Chen Dissertation, 2011

10 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)

11 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 C0.20822875.202E-05 B0.42992959.155E-05 DkDk 5.2163E-061.681E-06 D jk -6.0621E-071.940E-06 DjDj -3.2476E-089.333E-07 Ebb0.01658032.250E-04 Te8756.7911.693E-03 Exp Sim 1. Hirota, E. Ishiwata, T. Kawaguchi, K. Fujitake, M. Ohashi, N. Tanaka, I. J. Chem. Phys. 107, 2829 (1997)

12 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

13 Split Peak Analysis Split PeaksFrequencyWeighted PositionPredicted PositionWeight-Pred 18756.297 8756.3388756.3088756.313-0.004804 28759.787 8759.8308759.8158759.8080.006959 38761.049 8761.0838761.072 -0.000245 48761.741 8761.7778761.7518761.7500.000727 58762.638 8762.6618762.6498762.6480.001059 Fit Std Dev in MHzRMS Error in MHz 15882.70 Integrated ‘split’ peaks to find weighted position and compared it to the predicted position from the simulation.

14 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) 9/2 4 38763.43570.040361210 9/2 4 38763.3953 11/2 6 38772.81580.03511050 11/2 6 38772.7807 13/2 7 38778.83940.0286857 13/2 7 38778.8108 15/2 7 38778.94030.03581070 15/2 7 38778.9045 21/2 10 38802.176180.02178653 21/2 10 38802.1544

15 Conclusions We have obtained a high resolution spectrum of the previously unassigned 3 1 0 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 ~

16 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

17 Hirota A-State (4 1 0 )Uncertainty X-StateUncertainty B0.4330091.3E-05B0.4585752.2E-05 C0.21587055.0E-07C0.229288*** DNDN 1.433E-062.3E-08DNDN 1.256-064.9E-08 D NK -2.515-065.0E-08D NK -2.37-061.1E-07 DKDK 1.16975-06***DKDK 1.1495-06*** E bb 0.014981.6E-04E bb -0.016253.0E-04 Te7602.5754 Te0 Ming-Wei Chen A-State (4 1 0 )Uncertainty B0.432405E-05 C0.215276E-05 DNDN -2.54E-062.4E-07 E bb 0.01483E-04 Te7602.59232.3E-03 Constants Preliminary 3 1 0 Fit Excited StateUncertainty C0.20822875.202E-05 B0.42992959.155E-05 DKDK 5.2163E-061.681E-06 D NK -6.0621E-071.940E-06 DNDN -3.2476E-089.333E-07 E bb 0.01658032.250E-04 Te8756.7911.693E-03 Hirota, E. Ishiwata, T. Kawaguchi, K. Fujitake, M. Ohashi, N. Tanaka, I. J. Chem. Phys. 107, 2829 (1997)


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