On interpretation of infrared absorption lines

The interpretation procedures here for observations of ir absorption spectra recorded under conditions of low pressure and long path, assuming Lorentzian line shape, are treated with the help of a universal absorption contour. The central dip and slopes of the sides of the observed line contour are the measured quantities. An expression is given to correct for intruding wing absorption. The use of the line itself as a chopper to test validity of the Lorentzian line shape assumption is described.

Procedures for infrared spectroscopy

Three procedures are described: a modified Pfund triple-pass absorption cell; an improved image slicer; and new achromatic, doublet lenses. Design parameters for prism dispersion for various prism angles-both simple and composite prisms-are displayed by graphs. The relationships of dispersion and transmission are useful in designing prism spectrometers, predispersion systems for grating spectrometers, and LN-2 cooled predispersion systems for use with helium-cooled detectors. In combination with a suitable chopper they provide instrumentation suited to a study of the validity of the Lorentz line shape.

High resolution hadamard transform spectrometer

The ir spectrometer described employs alkaline halide lenses, an echelle grating, and a cryogenically cooled doped germanium bolometer as a detector. It is provided for two possible modes of operation: one is a single slit or conventional scan, the other is a multiplex or Hadamard scan. Signal strength, noise characteristics, scanning time, and available computer facilities determine the mode of operation. Sample spectra are presented.

Achromatic doublet lenses for infrared radiation

The indices of refraction and partial dispersions for the chlorides, bromides, and iodides of sodium, potassium, and cesium are suited for making diffraction-limited achromatic doublet lenses that are useful in infrared instruments. This paper describes the four best combinations (from seven materials). Together they cover the infrared over the range lambdalambda 1.5-38 micro. The performance of two lenses of optimized design (KBr-NaCl) is displayed by spot diagrams and test results. Applications of lenses, rather than mirrors, for compact optical systems are discussed.

Long-path study of infrared absorption and emission

The present status of a long-path absorption cell is described. The steel cell contains two mirrors of 91.4-cm aperture placed 30.5 m apart. End bells are utilized which permit operations at pressures ranging from 15 atm down to 10(-3) mm Hg pressure. The optical configuration of the mirrors within the tube as well as the transfer optics are described. Samples of the spectra being obtained are also discussed.

Objective transmission gratings for large schmidt telescopes

Several lamellar gratings of 18-in. aperture, with 300 diffraction elements per inch, have been made for determining stellar spectra with wide angle telescopes. Central orders are missing at lambda4800, and weak at adjacent wavelengths. The two, equal first orders are about l(m) weaker than spectra by a prism or echelette grating. Dispersion is linear. The procedure of manufacture is adaptable to larger size. The wavelength at which the central order is missing can be controlled by varying the lamellae thickness. The lamellae are evaporated strips of quartz of 0.5-micro thickness, covering half the face of the support-a spectacle crown, plane parallel plate of ?-in. thickness. The lamellae were deposited by thermal evaporation.

Bolometer theory

The theory of a thin bolometer strip is developed. It explains observation of enhanced response to spot illumination near the trip terminals, and predicts enhanced thermal fluctuation at the same point for uniform chopped illumination.

Balloon telescope optics

The article deals with optical problems associated with making infrared astrophysical observations with a balloon-borne telescope. Advantages and difficulties associated with such high altitude observations are reviewed. Topics treated are incandescence of components of the instrument in the infrared, infrared resolving power in the laboratory contrasted with that in the observatory; data documentation; collimator/planet-simulator; novel balloon telescope, and corrections of spherical aberration therein; vignetting and focusing; astigmatism correction; image slicer; grating spectrometer, and correction of aberrations therein; Benedictine slits; and detector-refrigerator and its optics.