Robert A. Oetjen

Spectral Radiance of Sky and Terrain at Wavelengths between 1 and 20 Microns. II. Sky Measurements

Quantitative data are presented to illustrate the infrared spectral radiance of the sky under a variety of situations. A qualitative discussion of the dominant spectral features is given to show the importance of the emission and scattering processes, the effect of angle of elevation, angle of azimuth, sun angle, and cloud cover.

An Infrared Spectrograph for Use in the 40–150-Micron Spectral Region*

Problems relating to the design of a far infrared spectrograph are discussed. The design of a spectrograph which was constructed is described. A platinum strip coated with thorium-oxide is used as a source. Discrimination against short-wave radiation is provided by quartz, paraffin, turpentine soot, a compensated potassium bromide chopper, reststrahlen plates, and a grating (used as a reflection filter) with groove separation somewhat less than the wavelength being investigated. As a dispersing device, an echelette grating ruled with 180 lines per inch is used. The detector is a Golay pneumatic cell. A low noise vacuum-tube amplifier renders the signal from the detector suitable for operation of a strip-chart recorder. The spectrograph is evacuable.Spectral operating characteristics of the instrument are shown in ammonia and atmospheric water vapor spectra in the region between 45 and 150 microns. Absorption lines separated by less than 1 cm−1 are well resolved throughout this spectral region.

Spectral Radiance of Sky and Terrain at Wavelengths between 1 and 20 Microns. I. Instrumentation

A description is given of a mobile laboratory equipped with two spectrographs for radiance measurements of the sky and terrain between 1 and 20 μ. The laboratory has its own ac power supply and means for controlling its temperature. Procedures are described for calibrating the instrumentation and transforming the data into spectral radiance (in microwatts cm−2 steradian−1 micron−1) as a function of wavelength.

The far infrared spectra of several pyramidal trihalides

Abstract The infrared absorption spectra of PCl 3 , PBr 3 , SbCl 3 , SbBr 3 , and AsCl 3 have been measured between 550 and 85 cm −1 using a grating spectrometer. The vibrational fundamentals have been assigned and force constants calculated on the basis of a four-constant potential function.

The Infrared Spectra of HCl, DCl, HBr, and NH3 in the Region from 40 to 140 Microns

The pure rotation spectra of HCl, DCl, HBr, and NH3 in the region from 40 to 140 microns as measured with an automatic‐recording grating spectrometer are presented in tabular and graphical form. A photograph of a recorded spectrogram provides an indication of the quality of the data. A comparison of the experimental results with figures based on accepted values of the molecular constants shows substantial agreement.

The Rotational Spectra of Regular and Deuterated Phosphine and Arsine in the Region between 50 and 200 K

The far infrared spectrograph at The Ohio State University was used to obtain the spectra of phosphine and arsine molecules. Tabular and graphical data show series of lines for phosphine, deuterated phosphine, arsine, and deuterated arsine in the ground vibrational state. Two previously unpredicted series of lines are clearly shown in the spectrum of phosphine and indicated in that of arsine. These additional series are ascribed to rotational transitions occurring while the molecules are in excited vibrational states and their rotational constants as well as the equilibrium rotational constants have been computed.

Spectral Radiance of Sky and Terrain at Wavelengths between 1 and 20 μ. III. Terrain Measurements

A mobile infrared spectrographic laboratory has been used to make absolute determinations of the apparent infrared spectral radiance of various types of terrain. The spectral distribution of the observed radiation indicates the predominance of reflected sun and sky radiation at wavelengths less than approximately 3 μ, and thermal emission at longer wavelengths. Examples are shown for a number of types of terrain observed in various locations and conditions. The transition between the sky and the ground is also illustrated by spectra taken near the horizon. The spectra of gypsum and silica sands show reststrahlen effects in the atmospheric window of wavelengths between 8 and 13 μ. Many of the features of the spectra of terrain can be explained, in some cases quantitatively, on the basis of known parameters of the particular background and its atmospheric environment.

The pure rotational spectrum of H2Se in the far infrared spectral region

Abstract The pure rotational absorption spectrum of H 2 Se has been measured in the spectral region between 40 and 250 cm −1 . From an analysis of the data, all the rotational energy levels of the ground state through J = 10 have been determined, and some higher levels have been assigned. The reciprocals of inertia for the ground state are found to be a = 8.16, b = 7.71, and c = 3.91 cm −1 . These values yield effective molecular dimensions r (H-Se) = 1.46 A and apex angle 2 α = 91.0°.

Designs of Photometer Units for Infrared Spectrographs

An attempt is made to obtain the design of a photometer unit which may be used with an infrared spectrograph so that percent transmission or some related quantity may be recorded directly. Several basic methods of accomplishing this are evaluated. It is concluded that the following should characterize the design: the optical system should be symmetrical; there should be only one path through the spectrograph; only one detector and amplifier should be employed; and these should actuate, through an appropriate servomechanism, a device to maintain equality of intensity in the two radiation beams, so that a null system results. Several possible basic designs for some of the components of the photometer are discussed.