AT-type electromagnetic shock tube [Elton, RC-,Griem, H.R, and Kolb, A.C., J. Opt. Soc. Am. 52:605 (1962)] was used for the detailed study of Stark broadened lines in the vacuum ultraviolet. Measurements of the Lyman-profile from an optically thin region (0.03 percent admixture of hydrogen in 40 mm-Hg helium) indicated agreement to within 10 percent with recent calculations [Griem, H.R., Kolb, A.C., and Shea, K.Y., Phys. Rev. 116:4(1959)] which included the broadening effects due to electron impacts, as opposed to the Holtsmark theory which differs by a fact of 3 on the wings when the theoretical curves are normalized at equal slope. A temperature of K has been determined from a line-to-continuum ratio measurement for helium. Density measurements from the visible continuum gave Ne = (3.6 + 0.4)10 The Rankine-Hugoniot equations predicted Ne = (4.8 + 1.9)10 andnT= K from the measured shock velocity. A calculated spectral emissivity of 0.09, 0.06 at 1217.7A compares with 0.l0 +0.02 as found experimentally by adding known amount of hydrogen until saturation occurs. It is thus possible to produce near-blackbody radiation from homogeneous plasmas of controlled optical depths. Such plasmas can possibly be used as intensity standards at other wavelengths in the vacuum ultraviolet by using other gases having strong lines appropriately spaced. Similar measurements on the Lyman- line support these results.
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