Electron Impact Excitation of the Rare Gases

Abstract

We utilize the analytic atomic independent-particle model (IPM) of Green, Sellin, and Zachor as a basis for calculating generalized oscillator strengths for the single-particle excitations of Ne, Ar, Kr, and Xe. First, we establish averages of the experimental energy levels to arrive at single-particle states. We then adjust the two parameters so that the IPM potentials accurately characterize these excited-state energies. Using the wave functions associated with these potentials and the Born approximation, we calculate the generalized oscillator strengths for excitations to p ns states. A very complex nodal structure is apparent at large values of momentum transfer and a rapid decline in magnitude occurs after the second node. We may accurately characterize the results up to the second node with a convenient analytic form which leads to analytic total excitation cross sections. We use available optical oscillator strengths to normalize our results. The systematics and regularities of the parameters for various Rydberg series are discussed and approximate scaling laws are given.

Optical oscillator strengths for the oxygen isoelectronic sequence

“…The parameters d and H are determined by requiring the energy eigenvalues to agree with the experimental single-particle energy levels which are obtained from the tables of Moore [7]. Since the IPM cannot distinguish between different states lying within a given multiplet, we replace each multiplet by an average value, following the procedure described in the work of Ganas and Green [8]. These averages serve as the experimental single-particle levels.…”

Electron impact excitation cross sections for O II

“…The formulas which are used to obtain the integrated cross sections from the GOS may be found in earlier work [6]. The computed integrated cross sections for various excitations from the 2p3 ground state, for incident energies ranging from threshold to 1 keV, are displayed in Figure 2.…”

Direct Nuclear Pumping by a Volume Source of Fission Fragments

“…15 The excitation cross sections for the optically allowed states 6s' [1/2]!, 6s[3/2] lf 5d [3/2],, and 5d[\/2] l were determined by the method of Ganas and Green. 16 The measurements of Kuprianov 17 were used to give the excitation cross sections for the metastable states 6s [ 19 and 20 were calculated using the method of Statz et al 21 ' 22 The excited states produced by the recombination of Xe are assumed to be 6/7, 7/7, and 5d, while those produced by the recombination of Xe 2 are assumed to be 6p [5/2] …”

“…The analysis presented here considers all He excited states with principal quantum number of 5 or less excluding the F states, 5d, 6s, 6s', 6/7, and Ip Xe excited states, ground state of Xe, four excited states of Xe 2 to allow for the formation of Presented as Paper 78-69 at the AIAA 16th Aerospace Sciences Meeting, Huntsville, Ala., Jan. [16][17][18]1978 dimers, He + , He + 2 , Xe", Xe~2, and e. Solution of the multifluid equations yields, among other things, the number densities of the preceding species and intensities. This makes it possible to calculate the gain coefficient and power output as a function of pressure, neutron flux, and mixture ratio for a given cavity.…”