STARK PROFILE MEASUREMENT OF THE LYMAN-ALPHA AND LYMAN-BETA LINES OF HYDROGEN,
Abstract
AT-type electromagnetic shock tube (Elton, R. C., 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-alpha 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 Shen, 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 factor of approximately 3 on the wings when the theoretical curves are normalized at equal slope. A temperature of 20,500=1,600 degrees K has been determined from a line-to-continuum ratio meas urement for helium. Density measurements from the visible continuum gave Ne (3.6-0.4)10 to the 17th power. The Rankine-Hugoniot equations predicted Ne (4.8=1.9)10 to the 17th power and T 20,000=1,000 degrees K from the measured shock velocity. A calculated spectral emissivity of 0.09=0.06 at 1217.7A compares with 0.10=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 appropriatedly spaced. Similar measure ments on the Lyman-beta line support these results. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 17, 1963
- Accession Number
- AD0418203
Entities
People
- R.c. Elton
Organizations
- United States Naval Research Laboratory