Differential elastic and total electron scattering cross sections of tetrahydrofuran

Differential elastic scattering cross sections of tetrahydrofuran for electrons were measured absolutely in the energy range from 20 eV to 1 keV at scattering angles between 5° and 135°. The measurements were carried out using a crossed-beam arrangement without the application of the widely used relative flow technique. The experimental differential scattering cross sections could be put on an absolute scale by means of the total electron scattering cross sections of tetrahydrofuran and of the current loss of the primary electron beam in the forward direction arising due to the scattering by the molecular beam. The total scattering cross sections were determined for electron energies between 6 eV and 1 keV using a separate linear transmission experiment. The differential cross sections of tetrahydrofuran for the elastic scattering of electrons were also calculated in the energy range between 60 eV and 1 keV by applying the modified independent-atom model. A comparison with the experimental results showed a satisfactory agreement, indicating that the selected theoretical model is adequate for these calculations.

Figure 1

Experimental (•) and theoretical ($-$) count rate of 1 keV electrons scattered elastically by helium at the scattering angle of 90° as a function of the kinetic energy for two pass energies: (a) 10 eV and (b) 100 eV. The peak heights were normalized to unity.

Figure 2

Schematic view of the experimental setup used for the measurement of the DCS in the scattering plane. The flow direction of the molecular beam is perpendicular to that of the electron beam and to the normal of the entrance plane of the hemispherical deflector. The scattering angle was adjusted by the rotation of the electron gun, and the beam stability monitor, a channel electron multiplier, was mounted at a distance of 15 cm from the scattering volume and at an angle of 15° relative to the electron-beam direction.

Figure 3

Angular dependence of $\Delta {\dot{N}}_{\mathrm{el}}\left(\theta \right)/\Delta \Omega$ ($⧫$) of 20-eV electrons scattered elastically by He. It was normalized to the DCS ($-$) of He proposed by Register et al. [13] at the scattering angle of 25°.

Figure 4

Dependence of the current loss $\Delta I$(◯) on the gas pressure $p_r$ in the reservoir over the gas tube and the best line fit ($-$) to $\Delta I/I$ vs $p_r$ for two electron energies: (a) 20 eV and (b) 100 eV.

Figure 5

Present results (◯) of the DCS of THF in comparison to the experimental data of Milosavljevic et al. [1] ($⧫$), Colyer et al. [2] (•), Dampc et al. [3] (▼), and Homem et al. [5] (▲), and to the theoretical values ($-$) obtained using the modified independent-atom model [23] for different electrons energies: (a) 20 eV, (b) 30 eV, (c) 40 eV, (d) 60 eV, (e) 80 eV, (f) 100 eV, (g) 200 eV, (h) 300 eV, (i) 400 eV, (j) 600 eV, (k) 800 eV, and (l) 1000 eV.

Figure 6

Relative contributions of the scattering terms appearing on the right-hand side in Eq. (10) to the theoretical DCS of THF for two electron energies: (a) 100 eV and (b) 1000 eV. The designation of the line types in (a) also applies to (b).

Figure 7

Schematic view of the experimental setup used for the measurement of TCS of THF.

Figure 8

Total electron scattering cross sections of THF as a function of the energy: (◯) present results, (■) Zecca et al. [6], ($⧫$) Możejko et al. [7], and (▲) Fuss et al. [8].

Figure 9

Experimental TCS (◯) of THF in comparison to the values (⋄) obtained from the TCS of C${}_2$H${}_4$ ($⧫$) [41, 42], CH${}_4$ (▽) [43], and CO (▲) [44, 45, 46] using the simple additivity rule.