Electron-scattering cross sections and stopping powers in ${\mathrm{H}}_2\mathrm{O}$

Total electron-${\mathrm{H}}_2\mathrm{O}$ scattering cross sections have been measured from 50 to $5000\mathrm{eV}$ with experimental errors of about 5%. Integral elastic and inelastic cross sections have been calculated over a broad energy range $(1–10000\mathrm{eV})$ with an optical potential method assuming an independent atom representation. Dipole rotational excitations have also been included in the framework of the first Born approximation. From a detailed evaluation of the present results and their comparison with previous theoretical and experimental data, a set of recommended integral cross sectional data is provided. By combining these data with an average excitation energy derived from the experimental energy loss spectra, the stopping power of electrons in ${\mathrm{H}}_2\mathrm{O}$ has been obtained from 5 to $5000\mathrm{eV}$.

Figure 1

(Color online) Experimental apparatus: 1, electron gun; 2, transverse magnetic field; 3, 7, quadrupole electrostatic plates; 4, 6, 8, decelerating and accelerating lenses; 5, scattering chamber; 9, hemispherical electrostatic energy analyzer; 10, channel electron multiplier; 11, 12 vacuum turbo pumps; 13 ion collecting plates.

Figure 2

Energy loss distribution function of electrons in water from 0 to $100\mathrm{eV}$.

Figure 3

Total electron scattering and ionization cross sections from ${\mathrm{H}}_2\mathrm{O}$. Present measurements: ▴, total scattering; ▵, ionization. Other measurements: ▷, [31]; ●, [36]; +, [30]; ○, [35]; ◇, [32]; ◆, [28]; ×, [22]. Calculations: - - -, present optical potential calculation; —, $R$-matrix calculation of [41].

Figure 4

Fano plot (total cross section multiplied by electron energy as a function of energy in a logarithmic scale): ●, present experimental data; ○, experimental data from [31]; - - -, present optical potential calculation; —, calculation of [40]; -$\bullet$- Born-Bethe calculation.

Figure 5

Mass stopping power of electrons in ${\mathrm{H}}_2\mathrm{O}$. ▴, present results; ◇, values given in NIST database [17]; gas phase calculations: — [48], -$\bullet$- [47]; liquid phase calculation: - - - [49, 50].