Total-cross-section measurements for electron scattering byNH3,SiH4

Abstract

Total cross sections for electron scattering have been measured in the 75 WOO-eV energy range for NH3, SiH4, and H2S. For these gases, as well as for CH4 and H20, cross sections have been fitted with a Born-like formula containing two parameters for each gas. The high-energy parameter of the fit to the cross sections has been related to the bond length of molecules. Partitioning of total cross sections into inelastic and elastic cross sections for these gases is discussed on the basis of available experimental data.PACS number(s): 34.80.Bm, 34.80.Gs

Phenomenology and scaling of electron scattering cross sections from “almost spherical” molecules over a wide energy range

“…If we hold this finding also for "almost spherical" molecules (compare Table 1 and [12]), the formula (3.4) would essentially point to an increase of the Ramsauer total cross 95 section with increasing polarizability a. We have not been able, to date, to make a convincing test of Eq.…”

“…A similar relation to that in Eq. (1.1), namely Ea = B, was earlier found by Zecca et al [12] for electron scattering from simple hydrides (CH 4, Sill 4, NH 3, H20, HzS) at high energies, beyond some "asymptotic energy", E z say. In that approximation a (E) tends to a constant value o'z for E~ E z.…”

“…Turning to high energies, for E > Ez (see Fig. 1 also) the regime of Zecca et al [12] is labelled Vin Fig. 2.…”

“…as shown in Table 1, with Ez the first ionization potential of the molecule and the "asymptotic energy" E z = B/a z has been calculated from the parameters given in [12] and [19].…”

“…1 shows a plot of data for CH 4 [1, 2,15], Sill 4 [12,16,17], GeH 4 [18], and CF 4 [19,20], using (Err) 1/2 as independent variable. Clearly, with the constant B used for scaling purposes, an "almost universal" curve results at high energies; the vertical slope there indicating the regime of Zecca et al [12].…”