1. Application of Cascaded Frequency Multiplication to Molecular Spectroscopy Brian Drouin, Frank W. Maiwald, John C. Pearson Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA 91109

2. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Current Tasks Temperature dependent air-broadened linewidths for EOS-MLS Ion rest frequency measurements for APRA Updating/Upgrading the JPL millimeter/submillimeter spectral line catalog Testing/implementing new technology for spectroscopy

3. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Technique Air, N 2, O 2 Vacuum Pump O 18 O, O 2 P P coolant out coolant in RF synthesizer Lock In Amp Frequency Modulation InSb Detector PT 100 cm 5 cm DC Power Supply PC DAQ quasi-optical lens 'top-hat' window vacuum rack multiplier T 0 o C

4. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer The Frequency Multiplication Submillimeter Spectrometer 83558A HP8340b SR830 M1611/2D HP FG AM/FM/TM sync InSb or Si gas pre-amp vacuum pump sample sweep synthesizer YIG filter mm-wave module MMIC amps submm multipliers waveguide feedhorns sample cell He cooled detector waveform generator lock-in-amplifier PC GPIB modulation DAQ tuning voltage

5. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Frequency Coverage “millimeter” 40 - 300 GHz –high power sources (4 almost cover band) –room temperature detectors (3-4 cover band) “submillimeter” 300 - 3000 GHz –new fixed tuned sources multiple configurations of multipler chains/amps for comprehensive coverage through 1000 GHz and bands near 1200, 1800, 2600 GHz –helium cooled detectors (InSb 1000)

6. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Broadband Frequency Coverage AMC-10 x6 0.07-0.11 THz MUTx2 0.15-0.24 THz MUTx3 0.18-0.28 THz VDI 1.9x5 0.38-0.58 THz VDI 1.5x6 0.58-0.69 THz VDI 1.2x10 0.76-0.88 THz JPL x2x2x3 0.85-0.95 THz JPL x2x2x3 1.05-1.25 THz JPL x2x3x3 1.57-1.67 THz 76.2% coverage up to 1.25 THz or 1.0 THz out of 1.6 accessible

7. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Multiplier Chains Rack containing RF Synthesizer, Function Generator, Lock-In-Amplifier & Power Supplies Sextupler and pentupler (600 GHz out) Sextupler, amplifiers, doubler, doubler, tripler (1200 GHz out)

8. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Harmonic Content VDI 1.9 x5: 98% x6 1% x7 1% VDI 1. 5 x6: 99% x4 1% VDI 1.2 x10: 100% JPL x2x2x3: >99% x2x2x2 <1% JPL x2x2x3: 99% x2x2x4 0.2% JPL x2x2x3x2 x2x2x3x3

9. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Source vs. Detector Noise Methanol features near 0.48 THz

10. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Broadband Methanol Spectra RA06

11. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Quantitative Rotational Spectroscopy Frequency/Quanta Assignments necessary –Fitted Hamiltonian –All thermal states useful (for partitioning) Dipole moment required –Linestrengths are typically known to high precision Linewidth helpful - integrated absorption vs. S/N Pressures in 0.1 - 2 Torr range with flexibility for strongest lines Can determine partial pressures of absorbers using direct absorption or calibrated FM Stability of direct absorption measurements is better than ever before! cross-sections concentrations contaminants

12. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer  = 0.095 cm -1 Torr -1 L = 4.5 cm p = 0.050 Torr 2.2% absorption HDO at 225 GHz  = 2.97e-18 cm 2 Observed 0.75% absorption indicating 1/3 of pressure is HDO, not surprising since the sample is a mixture of D 2 O and H 2 O

13. June 21 st, 2005Frequency Multiplier Submillimeter Spectrometer Thanks Tim Crawford Ed Cohen Herb Pickett John Pearson $$ HIFI/Herschel, APRA, UARP & EOS $$