The Visible Radiation from Helium in a Strong Shock Wave Page: 61
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where z * 1 and g = 1. For the gas in region 2 with T2, N, and <<2 &a
This amounts to about 0.14£ of the enthalpy per microsecond.
Recombination radiation may be divided into two limiting cases;
that which la blockaded and thus causes energy loss only near the surface
of the source, and that radiation to which the gas is essentially trans-
parent. When radiative recombination to the ground state occurs with
electrons having a moat probable kinetic energy of 1.9 ev, the radiation
will have a wavelength of about 470 A. According to Huang,5 the atomic
photo-ionization absorption coefficient, a, is about 5 x 10"*® ca^. Then
the distance required to re-absorb 90$ of this radiation is
Thus recombination to the ground state will not contribute appreciably to
radiative losses. Consider now recombination radiation to which the gas
is essentially transparent. The total rate of recombination to excited
• 2.5 * 10^ erg/cm3 jiaec
states for helium as given by Allen^ for a temperature of 22,000*K is
5S. S. Huang, Astrophya. J. 106, 354 (1944).
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Seay, Glenn Emmett. The Visible Radiation from Helium in a Strong Shock Wave, report, January 1957; Los Alamos, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc502356/m1/68/: accessed June 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.