Absorption of Sunlight by Atmospheric Sodium

Abstract

A photometer has been built which is sensitive to light only in a very narrow spectral region near the sodium D-lines. The light is scattered by sodium vapor at low density and the scattered light recorded by a photoelectric spectrometer. The latter resolves the two lines and allows the effect of stray light to be eliminated. With sunlight as the source, the radiation detected is at the bottom of the Fraunhofer lines and the residual intensity there may be measured. It is found that this intensity decreases slightly (relative to the continuum) as the sun approaches the horizon. This effect is attributed to atmospheric sodium; the amount found by this method agrees well with that deduced from twilight measurements. The thickness of the sodium layer in atoms/cm.2 varies between 3 and 9 × 109 in winter and is about 1 × 109 in April. The measurements also give the residual intensities of the Fraunhofer lines in the incident sunlight, averaged over the whole of the sun's disk. These are (5.90 ± 0.46)% for D1 and (5.06 ± 0.24)% for D2.

Pollution of the upper atmosphere by rockets

“…However, the following lines of reasoning may give some sort of sensible upper and lower bounds. Although Na has apparently not been detected in mass spectrometer experiments with rockets (JuNGE, OLDENBERG, and WASSON, 1962), it has been measured spectroscopically from the ground many times, and estimates of total free Na atoms per cm 2 column (HUNTEN and SHEPHERD, 1954;JONES and MCPHERSON, 1958;SCRIMGER and HUNTEN, 1957;MCNUTT and MACK, 1963;SULLIVAN and HUNTEN, 1964) range from 109 to about 8 x 109 cm -2. Both observation and theory indicate that these free atoms, which can be detected by their resonant scattering or absorption of sunlight, must have a maximum concentration at about 90 kin, and their concentration decreases very rapidly below this level, presumably because of rapid oxidation at the higher pressures.…”