Total cross section sodium

In Figure 2.15 we present the total cross sections for positron-sodium scattering. Shown here are the experimental data of Kwan et al. (1991) and Kauppila et al. (1994), and the theoretical coupled-state results of... 

Sodium has another advantage as a test for scattering and structure calculations. A very wide range of experimental data is available. This includes spin-dependent measurements of scattering and magnetic substate data, which will be described in chapter 9. In this section we consider only differential, integrated and total cross sections. 

Table 8.7. The integrated cross section a p for the 3p channel of electron—sodium scattering and the total cross section ot (ICr cm ). EXP (a-ip), interpolation in the data of Enemark and Gallagher (1972) EXP (oj), Kwan et al. (1991) CCO, coupled-channels-optical calculation (Bray et al, 199 Id)...

Determination of the total excitation cross section is again done by observing the resonance-line emission. Both the initial relative kinetic energy and the N2 temperature may be varied. First experiments of this type have studied the excitation of Na(3p) by N2, H2, and D2, vibrationally excited at 2000 to 3000°K for initial relative velocities from 1000 to 4000 m/sec l25-126 as well as both potassium and sodium.127 Recent studies with seeded beams 128131 on K + N2 and K + CO involved lower initial vibrational states v. This type of experiment is very difficult to analyze and evaluation invokes a number of assumptions for fitting the experimental data. A special threshold law for the energy dependence of the partial cross sections is adopted ... 

This apparently is based on the assumption that the cross-section depends on exp (-AEjkT). However, Frish and Bochkova141 claim to have demonstrated that the 8P state is produced only in very low yield. They observed the emission from excited sodium atoms in an electric discharge in He, Hg and Na mixtures at very low total pressures. Their data appear to show that the cross-section for excitation of the 8P state, the process with the smallest energy discrepancy and for which optical transitions of both atoms are allowed, is smaller than the cross-section into the 9S state, which is optically forbidden for the sodium. 

Fig. 2.15. Positron-sodium and electron-sodium total (and also for positrons partial) scattering cross sections. Experiment (positrons) o, Kwan et al. (1991) , Kauppila et al. (1994). Experiment (electrons) o, Kauppila et al. (1994). Theory , Hewitt, Noble and Bransden (1993) -----, Kernoghan (1996). Var-...

Fig. 4.21. Positronium formation in positron-sodium collisions. The experimental points are from Zhou et al. (1994b) the open and solid circles give the upper and lower limits respectively. Theory upper solid line, the cross section summed for nPS = 1 and nPS = 2, lower solid line with solid circles, cross section for nPS = 1, lower solid line with open circles, cross section for nPS = 2, all from the calculations of Hewitt, Noble and Bransden (1993) — —, total positronium formation cross section from Campbell et al. (1998a).

It has been measured for hydrogen (Fletcher et al, 1985 Crowe et al, 1990) and for lithium, sodium and potassium (Baum et ai, 1985) at incident energies from threshold to several hundred electron volts. The data were obtained by ionisation of polarised target atoms by polarised electrons. The relative total ionisation cross sections for parallel and antiparallel spins were determined by counting the ions, regardless of the kinematics of the final-state electrons. 

Neff measured excitation cross sections of resonance lines observed in meteors in collisions of Na", K+, Mg+, and Ca with N2 in a beam cell arrangement equipped with optical detection. The observed sodium D-line excitation cross sections are also shown in Fig. 12, and are approximately a factor of 3 smaller than the total charge transfer cross sections. 

FIG. 2.7 Relevant length scales for the colloidal structure of worm-like micelles contour length, Lc, entanglement length, /e, mesh size, m, persistence length, Zp and cross-sectional radius, rcs. Values shown are those measured for a solution with 1.5% total surfactant at a cetyltrimethylammonium tosylate (CTAT)/sodium dodecylbenzenesulfonate (SDBS) ratio of 97/3 with 0.10% added sodium tosylate. (Reproduced from Schubert, B.A., Kaler, E.W., and Wagner, N.J., Langmuir, 19, 4079 -089, 2003. With permission.)... 

Green maple cross sections (0.03 inch) were treated with aqueous NaOH at two concentrations for five minutes. The specimens were then lightly blotted, dried (total time out of solution was about one hour), ashed, and assayed for equivalent NaOH (Table I). The amount held by the xylan carboxyl groups (computed from calcium ion exchange value), of course, is independent of the external concentration. The amount held as sodium acetate should also be independent of the external concentration. The amount held in the lumen should be proportional to the external concentration provided equilibrium was established in five minutes of immersion in the aqueous NaOH. The sum of these component amounts should be the total equivalent NaOH in the treated wood provided none of the sodium acetate diffused out of the cross section during the five minutes. 

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