Experimental and theoretical cross sections for positron collisions with 3-hydroxy-tetrahydrofuran

Abstract

Cross section results from a joint experimental and theoretical investigation into positron scattering from 3-hydroxy-tetrahydrofuran (3H-THF) are presented. Total and positronium (Ps) formation cross sections have been measured from 1 to 190 eV using the positron beamline at the Australian National University, which has an energy resolution between 60 and 100 meV. The total cross section (TCS) and the elastic and total inelastic integral cross sections in the energy range between 1 and 1000 eV have been computed within the Independent Atom Model using the Screening Corrected Additivity Rule approach. In addition, we have calculated elastic differential cross sections at selected incident energies. Our computations represent the first theoretical results reported for this target species, while our measured Ps formation cross sections are also novel. Comparison of the present TCS with the previous results from the University of Trento shows a good level of agreement at the lowest energies. We also provide a comparison between the present cross sections for 3H-THF and those from our earlier study on the parent molecule tetrahydrofuran.

Total, elastic, and inelastic cross sections for positron and electron collisions with tetrahydrofuran

“…57 In those studies, reasonable agreement was found with the reported experimental results. In addition, we have also investigated the molecular systems NO 2 , N 2 O, 3-hydroxy-tetrahydrofuran, 58 and pyrimidine with our IAM-SCAR approach, and while the results from those studies are waiting to be written up for publication they are generally found to be in quite reasonable agreement with the available TCS data. As a consequence, we only briefly summarize the details of our positron-impact calculations here.…”

Cross sections for positron and electron collisions with an analog of the purine nucleobases: Indole

“…This is somewhat surprising, given the quite fair accord we have found between the IAM SCAR calculations and cross sections measured at Trento or the Australian Positron Beamline Facility [26,59,73] for some other large polyatomic molecules. We note, however, that for yet further targets the level of accord was not so good or not uniformly good at all energies [55,58,72]. Nevertheless, this large difference in indole between theory and experiment has only been seen for uracil [27] and in that case the discrepancy was almost certainly caused by inaccuracies in the temperature-vapor pressure curve that were used to derive the pressure from the measurements of the cell temperature.…”

“…We observe that the onset of the theoretical Ps formation channel occurs at somewhat higher energies than the known experimental threshold (Table I). As we noted in our earlier studies [55,72], this might reflect an intrinsic limitation in the current theoretical approach for representing the Ps formation channel.…”

Cross-section calculations for positron scattering from pyrimidine over an energy range from 0.1 to 10000 eV

“…Even though e + -pyrimidine TCS were measured by Zecca et al [24] only up to 50 eV, the trend of the last experimental values is to converge towards the theoretical curve. Recent experiments on positron scattering with the polar targets THF [82] and 3H-THF [83] tend to diverge from the earlier measurements performed by Zecca et al [84,85] at energies above Ps formation. Although no experimental explanation was given for these discrepancies, it may indicate that the TCSs from the Trento group are somehow underestimated in that energy regime.…”