Measurements of the curves-of-growth of hot water vapor
Hot water vapor curve of growth, using statistical band model with exponential line intensity distribution yielding spectral absorption coefficients
Ludwig, C. B.↗
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Spectral absorption of vacuum-pump fluids
Vacuum pump fluids spectral absorption coefficient measurement, using variable UV cell
Gillis, H. L.↗
Theory of pressure-induced vibrational and rotational absorption of diatomic molecules at high temperatures
Integrated absorption coefficient of pressure induced pure rotational and vibrational transitions in binary collisions of homonuclear diatomic molecules at high temperatures
Patch, R. W.↗
Comparison of the radiation flux profiles and spectral detail from three detailed nongray radiation models at conditions representative of hypervelocity earth entry
The radiation models were compared on the basis of the approaches used for the transport calculations and absorption coefficients and of results obtained for the radiation flux profiles and spectral distributions. The calculated results were for shock layer conditions representative of manned earth reentry from an interplanetary mission. The three models are RATRAP, RADICAL, and MDAC. The results show that significant differences exist in the radiation flux computed by the three models. The RADICAL model was found to depend on fewer approximations, to include more detail, and to require less computer time than the other models.
Suttles, J. T.↗
Transfer of thermal microwaves in the atmosphere, volume 1
The Mie theory is used to determine the absorption and scattering properties of liquid hydrometeors at 27 microwave frequencies from 500 MHz to 60 GHz. Based on the Marshall-Palmer distribution of drop sizes, regression equations are developed for the volume absorption coefficient of rain as a function of its temperature and content of liquid water.
Paris, J. F.↗
Effect of radiometric errors on accuracy of temperature-profile measurement by spectral scanning using absorption-emission pyrometry
The spectral-scanning method may be used to determine the temperature profile of a jet- or rocket-engine exhaust stream by measurements of gas radiation and transmittance, at two or more wavelengths. A single, fixed line of sight is used, using immobile radiators outside of the gas stream, and there is no interference with the flow. At least two sets of measurements are made, each set consisting of the conventional three radiometric measurements of absorption-emission pyrometry, but each set is taken over a different spectral interval that gives different weight to the radiation from a different portion of the optical path. Thereby, discrimination is obtained with respect to location along the path. A given radiometric error causes an error in computed temperatures. The ratio between temperature error and radiometric error depends on profile shape, path length, temperature level, and strength of line absorption, and the absorption coefficient and its temperature dependency. These influence the choice of wavelengths, for any given gas. Conditions for minimum temperature error are derived. Numerical results are presented for a two-wavelength measurement on a family of profiles that may be expected in a practical case of hydrogen-oxygen combustion. Under favorable conditions, the fractional error in temperature approximates the fractional error in radiant-flux measurement.
Buchele, D. R.↗
Results of measurement of radio wave absorption in the ionosphere by the AI method
Median noon absorption values for each month from 1964 through 1967, the diurnal variations of absorption on the regular world days, and the seasonal variations of absorption are given. The dependence of the absorption coefficient on sunspot number is analyzed.
Korinevskaya, N. A.↗
The influence of line shape and band structure on temperatures in planetary atmospheres
Numerical experiments are performed to examine the effects of line shape and band structure on the radiative equilibrium temperature profile in planetary atmospheres. In order to accurately determine these effects, a method for calculating radiative terms is developed which avoids the usual approximations. It differs from the more commonly used methods in that it allows arbitrary dependence of the absorption coefficient on wave number, without requiring tedious line by line integration and without the constraints of band models. The present formulation is restricted to homogeneous atmospheres but the concept can be extended to the more general case. The numerical experiments reveal that the line shape and band structure of the absorbing gases have a large effect on temperatures in the higher layers of the atmosphere (corresponding to the stratosphere and mesosphere). The more nongrey the spectrum (that is, the higher the peaks and the deeper the troughs in the spectrum), the lower the temperature.
Arking, A.↗
Optical absorption in fused silica at elevated temperatures during 1.5-MeV electron irradiation
An experimental determination of the optical transmission of Corning 7940 UV and Suprasil 1 and 2 fused silica has been made during 1.5-MeV electron bombardment. The fused silica reached temperatures ranging from 150 to 1000 C. The Lewis Research Center dynamitron provided electron current densities which corresponded to a dose rate of 2.6 to 20 Mrad/sec. The irradiation induced absorption was measured at 215.0, 270.0, and 450.0 nm (2150, 2700, 4500 A). The length of each irradiation was sufficient so that an equilibrium between radiation induced coloration and high temperature annealing was reached. The experimental results indicate a significant optical absorption, with values of the induced absorption coefficient at 215.0 nm (2150 A) of 14.5 to 2.2/cm, at 270.0 nm (2700 A) of 9.7 to 3.0/cm and at 450.0 nm (4500 A) of 3.7 to 0.5/cm. This would make the use of fused silica as the separating wall material in the nuclear light bulb propulsion concept questionable.
Smith, A. B.↗
Microwave emission from the moon
Measurements of the microwave emission from the moon and their interpretation in terms of the thermophysics of that body are reviewed. Variations of the brightness temperatures of the moon during a lunation and during eclipses when combined with infrared and radar measurements yield a precise set of physical parameters for the upper few meters of the lunar soil. These parameters include the density, thermal conductivity, dielectric constant, radio absorption coefficients, and the mean temperature gradiant.
Muhleman, D. O.↗
Stark-effect modulation of a CO2 laser by NH2D.
Use of the molecular Stark effect in NH2D to modulate the 10.6-micron P(20) line of a CO2 laser, yielding a modulation depth of 40% from a 200-V/cm rms signal applied to a 19.7-cm gas cell external to the laser. NH2D was prepared by mixing ND3 and NH3. The absorption coefficient of the M = 4 Stark-split line was measured as a function of mixing ratio and pressure. The observed pressure-broadening coefficient was 32.5 MHz/torr.
Johnston, A. R.↗
Total radiative intensity calculations for 100% H2 and 87% H2-13% He.
Isothermal radiative intensity calculations for 100% H2 and 87% H2-13% He are presented for temperatures of 10,000-25,000 K, density ratios of .0001 to .1, and path lengths of 1.0-30.0 cm. The actual spectral details of the absorption coefficient were computed for 16,000 points from 240 to 30,000 A by summing the various line and continuum radiative processes at each point. This method should result in a very accurate calculation of radiative emission, including an accurate accounting for reabsorption due to overlapping lines.
Stickford, G. H., Jr.↗
Photodissociation of CS2 in the vacuum ultraviolet - Determination of bond dissociation energy from the lowest vibrational level of the ground state CS2.
Photolysis in the vacuum ultraviolet results almost exclusively in the production of S(super-3)P atoms, which is in apparent violation of spin conservation. The threshold energy of incident photons required to produce fluorescence was used to calculate the bond dissociation energy (from the lowest vibrational level of the ground state), and the result agrees with the value previously derived from the photoionization of CS2. The fluorescence excitation spectrum shows peaks corresponding to Rydberg series I and II, indicating that the observed photodissociation of CS2 in the vacuum ultraviolet is mainly the result of predissociation from Rydberg states. The absorption coefficient of CS2 was measured in the region of 1200 to 1400 A.
Okabe, H.↗
Gyrosynchrotron radiation and its transfer in a magnetoactive plasma.
Gyrosynchrotron radiation fields from mildly relativistic electrons in a magnetoactive plasma are asymptotically calculated by using the Green tensor and the Fourier transformation. These fields consist of the two components which correspond to the ordinary and extraordinary modes. Taking into account these fields, the emissivities and the absorption coefficients from an arbitrary distribution of electrons are calculated in order to discuss the intensity, spectrum, and polarization of gyrosynchrotron radiation. In general, the transfer of electromagnetic energy takes place along a direction different from that of the wave normal since the radiation fields have a nonvanishing component along the direction of the wave normal. A consideration is given on the problem of radiative transfer in relation to the Stokes parameters.
Sakurai, K.↗
A sealed titanium window proportional counter for the detection of .5-keV X rays.
A sealed Ti window proportional counter sensitive to X radiation in the energy range 0.35-0.45 keV and above 1.5 keV is described. Measurements of the Ti mass absorption coefficients and a graphical summary of the literature values are presented. For a proportional counter with a 930 microgram/sq cm (2.1-micron) Ti window, the peak efficiency at 0.45 keV is found to lie between 4.6% and 7.1%. An application in X-ray astronomy involving a rocket observation of Sco X-1 is discussed.
Mcclintock, J. E.↗
Vibrational relaxation of the bending mode of shock-heated CO2 by laser-absorption measurements.
Study of the vibrational relaxation characteristics of shock-heated CO2 using a tuned CO2 laser absorption technique. Absorption-coefficient histories were obtained for a single rotational state in each of the -10 0- and -02 0- levels over the temperature range from 500 to 2000 K, and for 21 rotational states of the -10 0- level at 1000 K. These histories have been combined with translational-rotational temperature histories based on interferometer measurements to calculate vibrational relaxation times for the bending mode. The results verify the mutual equilibrium of the bending and symmetric-stretch modes due to Fermi resonance. The bending mode relaxation times are approximately 10% shorter than predicted from interferometer results using the ratio of specific heats. Furthermore, relaxation times based on measurements of different rotational states at 1000 K show a variation with quantum number J, indicating a possible rotational nonequilibrium during the vibration relaxation process.
Eckstrom, D. J.↗
The composition of the Martian atmosphere - Minor constituents.
The Mariner 6 and 7 infrared spectrometers provided data which, in principle, determine upper limits on the possible atmospheric abundance of every gaseous substance that was undetected but which has recognized absorptions in the accessible spectral region, 1.9 to 14.4 microns. Through supporting laboratory determinations of curves of growth under pressure-broadening conditions appropriate to Mars, upper limits can be specified (expressed first in cm-atm, STP, for a vertical column and then in parts per million) for NO2, NH3, C3O2, SO2, OCS, NO, O3, CH4, N2O, HCL, HBr, and H2S. In addition, considerations of band contours, moments of inertia, and experimental absorption coefficients make it possible to place useful upper limits on 27 additional substances that were not detected and for which curves of growth have not been measured.
Horn, D.↗
The prospects for mineral analysis by remote infrared spectroscopy.
An investigation of the effects of physical parameters on the spectra of minerals has been carried out, and an attempt made to develop a comprehensive theory of the reflectance (or emittance) spectra of particulate surfaces. The theory involves the effects of particle size, surface roughness, porosity, and mixing ratios on the spectra of mineralogical assemblages. The true spectral information is represented by the refractive indices and absorption coefficients of the constituent minerals. The present theory and the Mie theory for a cloud of well separated quartz particles are compared, as well as theoretical and experimental reflectances of quartz powders, glass beads, and corundum powders. Experimental results of abrading sapphire are presented.
Aronson, J. R.↗