1. A New E-Band (60 – 90 GHz) Fourier Transform Millimeter-wave Spectrometer DeWayne T. Halfen and Lucy M. Ziurys Department of Chemistry Department of Astronomy Steward Observatory Arizona Radio Observatory University of Arizona June 19, 2013

2. Why E-band ? U-band (40 – 60 GHz) upgrade very successful Takes the output of our existing 4 – 40 GHz system and multiplies (x2) up into 40 – 60 GHz Uses U-band (WR-19) waveguide components for radiation generation and detection and a smaller mirror Keep pushing the envelope of cavity-FTMW instrumentation Some molecules need measurements of higher transitions than covered in our current range –e.g. ScO (WH08) Designed a higher frequency band from 60 – 90 GHz, using WR-12 waveguide components with the same mirror

3. Original Fourier Transform Microwave Spectrometer Operated from 4 – 40 GHz 20 in. Al mirrors Quarter-wave antennas Pulsed valve at 40 o to Fabry-Perot cavity 22 in. cryopump Nd/YAG laser Laser Beam Internal window 20 in. mirrors Quarter-wave antennas

4. Block Diagram of New E-Band System  +  PIN Switch ++ 18.75-37.5 GHz   Computer Coupler Mixer Multiplier/ Amplifier LNA x2/x4 Amplifier LPF x2/x4 Amplifier Multiplier/ Amplifier Coupler RF Detector A/D 60-75 GHz 75-90 GHz

5. E-Band System Diamond-cut Al mirrors with inner Brass plug –170 mm (6.7 in.) diameter with 838 mm (33 in.) radius of curvature –Incorporated into existing vacuum chamber and spectrometer setup Replaced WR-19 devices with WR-12 components Use a JPL/NRAO MMIC Low Noise Amplifier (LNA) (E. Bryerton)

6. Radiation Source Active Doubler or Quadrupler Isolator Waveguide Coupler Cu Mounting Plate WR-19 to WR-12 Transition

7. Detection Electronics Active Doubler or Quadrupler IsolatorLNA Coupler Mixer RF Detector Waveguide Coupler Cu Mounting Plate WR-19 to WR-12 Transition Isolator

8. Detection Electronics Active Doubler or Quadrupler Isolator LNA Coupler Mixer RF Detector Waveguide Coupler Cu Mounting Plate WR-19 to WR-12 Transition Isolator

9. Cavity Mode Structure Only prominent cavity modes – q modes spaced every half wavelength apart –~2 mm in mirror distance or 80-100 MHz in frequency space –Overtone q modes more prominent in E-band than U-band Q factor around 100,000 from 60 – 90 GHz –Q for 40 – 60 GHz – 80,000 – 100,000

10. Tested system on OCS and its isotopologues (0.5 % OCS in Ar) First Light Spectra

11. Used Discharge-Assisted Laser Ablation Source (DALAS) Steel ablation adapter with Teflon discharge nozzle Metal vapor mixed with dilute reactant gas in Ar DC discharge Gas Phase Synthesis Motor Housing Metal Rod Discharge Nozzle Pulsed Valve Ablation Adapter Docking Station Metal Rod

12. Also recorded spectra for AlO, VO, NiC, and ScC 2 Free Radical Spectra Al vapor + 0.1 % N 2 O in Ar, no DC V vapor + 0.1 % N 2 O in Ar, no DC Ni vapor + 0.5 % CH 4 in Ar, 600 V DC 5000-10000 shots Sc vapor + 0.5 % CH 4 in Ar, 1000 V DC

13. 60 – 90 GHz FTmmW system successfully constructed using waveguide devices Mode structure very clean Spectra with high S/N ratio obtained More data from this system presented next –ScO – WH09 Build separate spectrometer to utilize U and E-band systems Conclusions and Future Directions

14. Acknowledgements Lucy Ziurys Aldo Apponi Bob Freund Jessica Edwards Jie Min Gilles Adande Matt Bucchino Julie Anderson Debbie Schmidt NSF NASA