Schematic diagram of an unrolled segment of DNA with the THF molecule highlighted in the phosphate-deoxyribose backbone structure.
(a) The present experimental TCS for positron scattering from THF (●) are compared to those from Zecca et al. 22 (□). Note that for clarity the overall error bars on the present experimental TCS between 6 and 60 eV are shown at some selected energies only. The present measured TCS corrected for forward angle scattering (○) are also given at selected energies (see Table I ). Also plotted are the present positron (———) and electron (– – –) impact TCS calculated with our IAM-SCAR method, as well as the computed positron (−·−·−·) and electron (−·· − ·· − ··) impact IAM-SCAR TCS also including the Born dipole-induced rotational excitations. Shown also are the electron-impact TCS measured by Mozejko et al. 23 (■) and computed by Bouchiha et al. 32 (- - -). (b) Same as (a) but in log-log scale.
The present measured Ps formation cross section (●) and summed inelastic ICS for electronic excitations and direct ionization (■). Also shown is the sum of the Ps formation cross section and the inelastic ICS (♦) at the common positron energies, in order to compare to the current IAM-SCAR computed sum over all inelastic ICS (———) except rotations and vibrations. Note that for clarity the overall error bars on the present experimental Ps formation cross sections between 6 and 50 eV are shown only at selected incident energies.
Example of a RPA curve measured with THF vapour in the scattering cell at a scattering energy of 30 eV and with a ratio B SC/B RPA = 5. The red (– – –), green (— — —), and blue (−·−·−·) vertical lines indicate the threshold energies for the end of the quasi-elastic scattering region, the first electronic singlet state and the first ionization potential in THF, respectively. Shown also are the estimates for the fraction of the inelastic to total scattering occurring between the opening of the first electronic excitation and the onset of direct ionization, as well as that taking place above the first ionization energy onwards.
The present measured (●) and calculated (———) quasi-elastic DCS for positron collisions with THF at selected incident energies: (a) 1 eV, (b) 5 eV, (c) 10 eV and (d) 20 eV. We show the present IAM-SCAR results that include the contribution of rotational excitations in order to consistently compare to our measured quasi-elastic DCS (see text). Plotted also are the electron-impact DCS results from the measurements of Allan 26 (— — —) and the SMC computations with Born-dipole correction of Gauf et al. 29 (−·−·−·).
Estimates of the missing angular range (0° ± θ min) in the present measured TCS, and of the corresponding correction for the forward angle scattering effect. That latter correction was calculated with the present IAM-SCAR elastic DCS, with Born dipole-induced rotational excitations (see Table VI ), at selected positron scattering energies.
The present measured TCS (σ T), Ps formation cross section (σ Ps) and summed inelastic ICS for electronic excitations and direct ionization (σ I), together with their overall uncertainties (Δσ).
The present TCS (σ T), elastic (σ E) and summed inelastic ICS (σ I) (except rotations and vibrations) for positron scattering from THF calculated with our IAM-SCAR approach. Also given are the ICS for the Born dipole-induced rotational excitations (σ rot) and the TCS that includes those cross sections (σ T + rot).
The present TCS for electron scattering from THF computed with our IAM-SCAR method, both without (σ T) and with (σ T + rot) the Born dipole-induced rotational excitation cross sections.
The present measured elastic DCS for positron collisions with THF, as a function of the scattering angle at the incident positron energies investigated. Also shown are the overall error bars.
The present elastic DCS for positron scattering from THF calculated with our IAM-SCAR approach, with Born dipole-induced rotational excitations, at selected scattering energies.
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