New assignments in the submillimeter emission spectrum of the stratosphere

New line assignments in the spectrum of the stratospheric submillimeter emission, measured with unapodized resolution of 0.0033 cm^–1, have been made. Positive evidence for the presence of symmetric and asymmetric ozone isotopes, water vapour excited to the (010) level, and HCN is given.     

Dielectric measurements in the submillimeter wavelength region

The paper describes a method for dielectric measurements in the submillimeter range based on the application of a backward-wave-oscillator technique. The application of submillimeter dielectric spectroscopy for solving real problems of solid-state physics is discussed.     

The submillimeter wavelength spectrum of methanol

Observations and assignments of some of the absorption lines in methanol from 200 to 850 GHz are reported. A simple phenomenological model is described which allows interpretation of spectra and prediction of new lines with little computational effort.     

High resolution molecular spectroscopy in the submillimeter region

Fourier Transform laboratory measurements have been carried out, for the first time in the 8–85 cm^–1 spectral region, with an unapodized resolution of 3.3. 10^–3 cm^–1 and a frequency accuracy of 2. 10^–4 cm^–1. Samples from spectra of several molecules namely: CO, O₃, H₂O₂, NO, NO₂, HNO₃, SO₂, H₂S, HOCL, NOCL, HNCO, ND₃ and AsH₃ are presented to show both the quality of the measurements and the type of information supplied by high resolution spectroscopy in the submillimeter region.     

An evacuable open resonator operating in the submillimeter region

Conclusion A new evacuable open resonator operating at 337 m wavelength has been described. Some preliminary results for the refractive index of dry nitrogen give a value at variance with previously published values. Investigations have shown an unexpected pressure induced change in cavity length, rather than contamination by other gases, to be the cause of the discrepancy. The cause of this effect is being thoroughly investigated and when it has been overcome it is hoped that this apparatus can be used to make measurements of refractive index and attenuation coefficients throughout the submillimetre region.     

Study for second harmonic gyrotrons in the submillimeter region

Calculations related to the high frequency, step tunable gyrotrons designed to operate in the submillimeter region, as reported by workers at Fukui University and the University of Sydney are presented. The modes probably have a rotating structure, in general. Results for mode competition are very similar to those calculated previously, in spite of the rather different calculational method.     

On the anomalies in submillimeter absorption spectrum of atmospheric water vapor

Using a tunable source of monochromatic radiation (BWO) and a pneumatic detector, the field and laboratory investigations have been performed to obtain spectral distribution of atmospheric water vapor absorption coefficient in transparent windows centered at the wavelengths of 0.88 and 0.73 mm.The measurements have not found any spectral features mentioned repeatedly in the literature, besides the usually observed excess of the measured absorption above the calculated one for water vapor monomers.     

The millimeter and submillimeter rotational spectrum of 1,3-dihydroxyacetone

Recent detection of the 2C sugar glycolaldehyde in the Sgr B2(N-LMH) hot core source as well as the presence of several sugars and other polyhydroxylated species in the Murchison meteorite have led to interest in observational searches for higher order sugars in the interstellar medium. 1,3-Dihydroxyacetone, the simplest 3C sugar, is one of the species detected in Murchison and is of considerable importance for observational searches as the next step in complexity for interstellar sugars. However, little spectroscopic information is available for this molecule. We present here the Doppler-limited rotational spectrum of 1,3-dihyroxyacetone to 450 GHz. Assignments include the ground state up to J=104 and four additional vibrational states. Standard rotational and quartic centrifugal distortion constants have been determined for each of these states.     

Interference filters for the millimeter and submillimeter spectral region

The properties of a Fabry-Perot interferometer (FPI) with mirrors in the form of metal gratings are discussed. For obtaining filters for the submillimeter and millimeter spectral region we suggest the use of an interferometer with crossed gratings, each grating being enclosed between dielectric plates. Our studies have shown that the half-width of the transmission band of such a filter amounts to 0.6 mm at =8.4 mm, the transmissivity being 77%.In conclusion, the authors wish to express their gratitude to M. A. Leontovich for valuable discussions and to V. D. Rusanov and V. M. Plekhov for their collaboration in the work.     

Investigations of the apparent temperature of snow cover in the submillimeter wavelength region

Equipment and methods used for measuring the apparent temperature of snow cover in high mountains is described. The spectrum of dry snowpack emission in the wavelength region 0.85÷1.3 mm is obtained. The dependence of the apparent temperature of snow cover on the atmospheric optical depth is determined. It is shown that in the first approximation the snow cover emission is described by the Lambert law and the snow albedo is within 0.6÷0.67.     

Optimization of a schottky barrier mixer diode in the submillimeter wave region

We have designed a mixer Schottky barrier diode (SBD) for use in the submillimeter wave region with a structure optimized for minimum noise temperature. The dependence of mixer noise temperature upon thickness and doping density of the epitaxial layer and diode diameter of SBDs was simulated within the framework of existing theories. Special care was taken to formulate the SBD current-voltage and capacitance-voltage relations in a way that correctly describes the behavior of real SBDs.     

Prediction of the submillimeter spectrum of the cosmic backgroundradiation by a plasma model

A non-Big-Bang plasma model is used to predict the submillimeter spectrum of the cosmic background radiation (CBR). Early intermediate-mass stars heat dust which, in turn, warms electrons trapped in force-free filaments emitted by galactic nuclei. Current stars contribute further heating by the same synchrotron mechanism. The electrons emit a nonblackbody radiation which matches the observed CBR spectrum and isotropy. The model also predicts intergalactic absorption of radio radiation, as confirmed by observations of spiral galaxies, and accurately predicts the spectrum of radio-quiet sources     

Millimeter and submillimeter wave rotational spectrum of pyridine in the ground and excited vibrational states

The pure rotational spectra of the ground and five excited vibrational states of pyridine were measured, assigned and fit in the 75-110 and 260-370 GHz frequency bands. An improved set of spectroscopic constants was obtained for the ground state, and all the rotational and quartic centrifugal distortion constants were obtained for the excited vibrational states.     

Single mesh narrow bandpass filters from the infrared to the submillimeter region

Narrow bandpass filters from i.r. to Submillimeter have been investigated utilizing the bandpass transmission characteristic of an electroformed metal mesh around the wavelength near the grid constant (ɡ). The bandwidth was narrowed by controlling the strip breadth of the mesh. It was found experimentally that the mesh having the strip breadth equal to half the grid constant was best.Filters with 25 mesh (ɡ = 1016 μ), 50 mesh (ɡ = 508 μ), 100 mesh (ɡ = 254 μ), 250 mesh (ɡ = 101.6 μ). 500 mesh (ɡ = 50.8 μ), 1000 mesh (ɡ = 25.4 μ) and 1500 mesh (ɡ = 16.9 μ) have been measured, keeping each strip breadth at the best condition, and narrow bandpass filters from i.r. to submillimeter have been constructed. Most of these filters have maximum transmittance around 70% and Q-value of about 4.These filters have some advantages over Reststrahlen filters and are useful for many spectroscopic studies.     

The millimeter and submillimeter spectrum of CN in its first four vibrational states

The rotational absorption frequencies of 65 new lines in the millimeter and submillimeter region of the spectrum have been measured for the CN radical in its ground electronic state. These measurements were made in a low pressure glow discharge of methane and nitrogen and include 25 lines from the v = 2 and v = 3 vibrational states, in addition to 40 lines from v = 0 and v = 1. The Dunham constants, as well as the spin-rotation and hyperfine constants of these four vibrational states, were calculated by means of a global nonlinear least squares fit of these data.     

Reflectance characteristics in the submillimeter and millimeter wavelength region of a vacuum compatible absorber

The reflectance characteristics of a grooved sample of Corning Macor, a glass ceramic, were studied in the range 60–1100 GHz for incident and reflected angles ranging from 10° to 65°. Measurements indicate a low, <1%, reflectance for near normal angles of incidence, where the angles of incidence and reflection are defined with respect to a direction normal to the sample face as if it were a planar surface. Higher values, up to 6%, were obtained for other angles of incidence and these results depend upon the orientation of the sample grooves with respect to the polarization of the electric field of the incoming radiation. Structure in the spectra indicates complex interference effects in some configurations.