A Large Throughput High Resolution Fourier Transform Spectrometer for Submillimeter Applications

We have designed and constructed a Fourier Transform Spectrometer (FTS) for the study of submillimeter-wave mixers and optical components. The FTS has a large aperture (up to 25.4 cm) and small focal ratio (as fast as f/2.5) to achieve a large throughput. It operates in the 100-3750 GHz (3.3125 cm \Gamma1 ) frequency range with a resolution of up to 75 MHz (0.0025 cm \Gamma1 ). Here we discuss the design goals and provide a detailed description of the construction of the FTS. In addition, we highlight the variety of studies which have been conducted with this instrument, which include characterizing SIS mixers through both direct and heterodyne detection and measuring the properties of optical materials. keywords: Fourier Transform, spectroscopy, quasi-optics, heterodyne, SIS, dielectrics, submillimeterwaves, material properties 1 Presently at TeraDyne, 30801 Agoura Rd., Agoura Hills, CA 91301 2 Presently at JPL, Mail Stop 168-314, Pasadena, CA 91109 3 Presently at Bach Corpor..

Atomic Carbon and CO Isotope Emission in the Vicinity of the Orion Bar

. We present observations of the 3 P1! 3 P0 fine structure transition of atomic carbon, as well as of the J = 2!1 transition of 13 CO and C 18 O toward the Orion Bar, the south-- eastern rim of the cavity carved out in the Orion molecular cloud by the H ii region surrounding the Trapezium stars. The Orion Bar is a dense region illuminated by an intense flux of UV photons, i.e. a photodissociation or photon--dominated region (PDR). The observed C i intensity agrees with models of uniform--density edge--on PDRs, which predict a spatially stratified morphology for the ionized, neutral, and molecular components. Our observations, however, show a surprisingly good spatial correlation between C i and 13 CO. The bright neutral carbon and 13 CO emission from the Bar is superposed on a broad plateau of extended emission. The origin of this extended distribution may lie in the particular geometry of the region, which gives rise to face-on PDRs associated with the back and front wall..