Submillimeter wave/THZ technology and rotational spectroscopy of several molecules of astrophysical interest

A compact, high resolution spectrometer operating in the millimeter and submillimeter wave range has been developed based on concepts of signal detection and understanding of the molecular systems whose study is desired in numerous applications. The novel FASSSTER (FAst Scan Submillimeter Spectroscopic Technique with Electronic Reference) technique employs electronic frequency markers for frequency calibration. The new frequency calibration scheme replaces the optical calibration used by the existing FASSST spectrometer. Moreover, the small size, low power consumption, and the potential of very low cost make this approach attractive for a number of important applications.; A number of improvements and modifications in the realm of software and hardware have been introduced to the existing FASSST spectrometer. The accuracy of the frequency calibration is now comparable to the accuracy of the spectrometers using more traditional principle of PLL (Phase Lock Loop) frequency stabilization and source modulation.; The approach presented for the assignment of rovibrational spectra, CAAARS (C&barbelow;omputer A&barbelow;ided A&barbelow;ssignment of A&barbelow;symmetric R&barbelow;otor S&barbelow;pectra), provides an integrated tool to simplify and speed up spectral analysis. CAAARS combines visual, interactive, mouse-assisted line assignment with real-time fitting of the assigned transitions to the spectroscopic constants of an appropriate rovibrational Hamiltonian. The ease of operation and flexibility in the choice of an appropriate theoretical model make it a powerful tool in the hands of a spectroscopist. Its advanced user interface, capable of displaying multiple traces of the experimental spectrum for unambiguous line identification, is a logical extension of the Loomis-Wood approach to line assignment. CAAARS implements user-specified sorting to select subsets of the predicted transitions for transparent assignment and manipulation. The current version of CAAARS is available for downloading at http://www.physics.ohio-state.edu /∼medvedev/caaars.htm.; The room temperature millimeter and submillimeter wave spectra of diethyl ether (C2H5OC2H5), oxiranecarbonitrile (H2COC(H)CN), and ethyl formate (HCOOC2H5) were measured using FASSST (FAst Scan Submillimeter Spectroscopy Technique) spectrometer. The vibrational ground states of the oxiranecarbonitrile, trans and gauche conformers of ethyl formate, and trans-trans and trans-gauche conformers of diethyl ether were analyzed. The results of this investigation can now be used for identification of diethyl ether, oxiranecarbonitrile, and ethyl formate in the interstellar medium.