Normalisation cross section measurements

Experimental differential cross sections are put on an absolute scale by first normalising to the differential cross section for the first dipole transition (3p). The integrated cross section for this transition is determined by numerical integration using differential cross sections measured as close to 0 = 0 as possible, supplemented by shape extrapolation based on a calculation. Integrated cross sections are determined in ways that ultimately depend on measurements of the optical oscillator strength (5.84). They... 

Another commonly-used normalisation procedure is to use the relative flow technique. In this method the elastic differential cross section for a particular species may be obtained by comparing the scattered intensity under the same conditions with that from another target with a known cross section. It is important to ensure, for both the gas under study and the reference gas, that the electron flux density and distribution, the detector efficiency, and the target beam flux distribution are the same for both gases during the measurement. 

The total ionisation cross section for hydrogen has been measured by Shah et al. (1987) in a crossed-beam experiment. Slow ions formed as collision products in the interaction region were extracted by a steady transverse electric field. H+ ions were distinguished by time of flight. Relative cross sections were normalised to previously-measured cross sections for hydrogen ionisation by protons of the same velocity. The proton cross sections were normalised to the Born approximation at 1500 keV. 

The distorted-wave impulse approximation using Hartree—Fock orbitals is confirmed in every detail by fig. 11.5, which shows momentum profiles for argon at =1500 eV. The whole experiment is normalised to the distorted-wave impulse approximation at the 3p peak. It represents the remainder of the confirmation in this case of the whole procedure of electron momentum spectroscopy. The Hartree—Fock orbitals give complete agreement with experiment for two manifolds, 3p and 3s. The spectroscopic factor Si5.76(3p) is measured as 1, since no further states of the 3p manifold are identified. Later experiments give 0.95 and this is the value used for normalisation. The approximation describes the momentum-profile shape for the first member of the 3s manifold at 29.3 eV within experimental error. The shape for the manifold sum of cross sections agrees and its... 

The quantity x = MG/M is the mass quality or simply quality in the flow at a cross section of the tube. This equation reproduces the measurements for water, refrigerants Rll, R12, R113 and methanol, ethanol, benzene, toluene and trichloroethylene in condensation in vertical, horizontal and inclined tubes with 7 to 40mm internal diameter, at normalised pressures 0.002 < p+ < 0.44, saturation temperatures 21°C < i9s < 310 °C, vapour velocities 3m/s < wG < 300 m/s, mass fluxes 10.8kg/m2s < m < 210.6 kg/m2s, heat fluxes 158 W/m2 < q < 1.893 106 W/m2, Reynolds numbers 100 < Re < 63 000, and Prandtl numbers 1 < Pr < 13. The mean deviation from the experimental values has been shown to be 15.4 %. 

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