1. DEVELOPMENTS IN FAST SCAN SUBMILLIMETER SPECTROSCOPIC TECHNIQUE (FASSST) AND COMPUTER AIDED ASSIGNMENT OF ASYMMETRIC ROTOR SPECTRA (CAAARS) SOFTWARE SUITE. IVAN R. MEDVEDEV, FRANK C. DE LUCIA, AND PAUL HELMINGER

2. Interference fringes Spectrum InSb detector 1 InSb detector 2 Ring cavity: L~15 m Mylar beam splitter 1 Mylar beam splitter 2 High voltage power supply Slow wave structure sweeper Aluminum cell: length 6 m; diameter 15 cm Trigger channel /Triangular waveform channel Signal channel BWO Magnet Lens Filament voltage power supply Length ~60 cm Stepper motor Reference channel Lens Stainless steel rails Path of microwave radiation Preamplifier Frequency roll-off preamplifier Reference gas cell Glass rings used to suppress reflections Data acquisition system Computer FAst Scan Submillimeter Spectroscopic Technique (FASSST) spectrometer

3. Effect of atmospheric dispersion on frequency calibration accuracy

4. Strategy to overcome atmospheric absorption at higher frequency -Purging of FP cavity reduces the effect of atmospheric absorption -Higher frequency BWO oscillator tube are less well behaved

5. 260 GHz 375GHz

6. InSb detector 1 InSb detector 2 Ring cavity: L~15 m Mylar beam splitter 1 Mylar beam splitter 2 Aluminum cell: length 6 m; diameter 15 cm BWO Magnet Lens Length ~60 cm Stepper motor Lens Stainless steel rails Path of microwave radiation Reference gas cell Glass rings used to suppress reflections FAst Scan Submillimeter Spectroscopic Technique (FASSST) spectrometer

7. THz spectrum of Nitric Acid

8. Experimental Signal/Noise Ratio of ~1000 allows us to resolve transitions with energies ~1500 cm -1 above ground state. Line shape and sensitivity

9. Heating and Cooling Capabilities of the FASSST spectrometer MH08 - SARAH M. FORTMAN

10. COMPUTER AIDED ASSIGNMENT OF ASYMMETRIC ROTOR SPECTRA (CAAARS) SOFTWARE SUITE. i. CAAARS is flexible software package designed for assignment of ro-vibrational molecular spectra. ii. Point and click approach to line assignment iii. The flexible sorting principle makes CAAARS applicable to a wide range of spectroscopic problems iv. The organization of the predicted and assigned lines into branches allows the user to plot easily Fortrat diagrams, intensity plots, R- or P-branch clusters, (K a or K c vs. frequency for a given J), errors, reduced energy plots, perturbed branch behavior, and whatever else is found useful for a given spectrum. v. Compatible with SPFIT/SPCAT as well as ERHAM (Peter Groner) vi. Latest version requires Igor Pro version 6 software package for operation vii. Available for downloading from http://www.physics.ohio-state.edu/~medvedev/caaars.htm

11. CAAARS user interface employing Fortrat diagram

12. Conclusions i.Spectral coverage of the FASSST spectrometer has been extended to frequencies surpassing 1 THz ii. Optical cavity employed by the spectrometer for frequency calibration now can be reliably purged with dry N 2 iii.Absorption cell of the FASSST spectrometer can now be uniformly cooled and heated to a wide range of temperatures iv.CAAARS software package has been further tested and improved. The latest release is available for downloading at http://www.physics.ohio-state.edu/~medvedev/caaars.htm