Total cross sections for positron and electron collisions with NH<sub>3</sub>and H<sub>2</sub>O molecules

Sueoka, Osamu; Mori, Shigeki; Katayama, Yoshifumi

doi:10.1088/0022-3700/20/13/028

Cited by 67 publications

(65 citation statements)

References 12 publications

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“…1a,b we see that for e-NH 3 scattering, the total cross sections of SEF, ADR, SCOP [6] and the results of Joshipura and Patel [7] agree above 200 eV. They also agree well with the experimental results reported in [8] [12] in this energy range, but are slightly larger than the results reported by Sueoke et al [10]. Below 200 eV, the four theoretical calculations show discrepancies.…”

Section: The Results and Discussionsupporting

confidence: 77%

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Total cross sections for electron scattering from molecules: NH3 and H2O

Liu

Sun

et al. 1997

Z Phys D - Atoms, Molecules and Clusters

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By developing the semi-empirical formula recently obtained for total cross sections of electron scattering from diatomic molecules in the intermediate-and highenergy range, we calculate the total cross sections for electron scattering from molecules (NH 3 and H 2 O) over an incident energy range of 10-1000 eV. The total cross sections have also been calculated by using the complex optical potential and the additivity rule. Compared with other available experimental and calculating data, excellent agreements have been achieved. The developed semi-empirical formula reflects that total cross sections for electron scattering from NH 3 and H 2 O in the intermediate-and high-energy range quantitatively depend on the bond length.

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Section: The Results and Discussionsupporting

confidence: 77%

“…Zecca et al [8] [9], Sueoka and coworkers [10] [11], Garcìa and Manero [12] have measured the total cross sections for electron scattering from H 2 O and NH 3 in different energy range. Comparison with theory reveals a quite large discrepancies as far as characteristic features of the σ(E) curves are concerned.…”

Section: Introductionmentioning

confidence: 99%

Total cross sections for electron scattering from molecules: NH3 and H2O

Liu

Sun

et al. 1997

Z Phys D - Atoms, Molecules and Clusters

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“…However, polarization often enhances direct ionization by positrons, so that they can be more penetrating and more ionizing than electrons, a result of potential import in analyses of astrophysical (e.g., [8]) and atmospheric events (e.g., [9]) as well as in positron-track simulations for dosimetry in positron emission tomography (e.g., [10]). In turn, these studies contribute to the motivation for investigating the interaction of e þ with water which accounts for about 60% of the human body and which is the most abundant greenhouse gas in the atmosphere.Measurements of positron-water total cross section (σ T ) were first carried out 30 years ago [11,12]. Since then, only a few new results have been added, experimentally [13][14][15] and theoretically [16,17], without a satisfactory agreement emerging among them.…”

mentioning

confidence: 99%

“…Measurements of positron-water total cross section (σ T ) were first carried out 30 years ago [11,12]. Since then, only a few new results have been added, experimentally [13][14][15] and theoretically [16,17], without a satisfactory agreement emerging among them.…”

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confidence: 99%

“…Detection of FSPs leads to a systematic underestimate of the beam attenuation and, thus, the measured total cross sections. In this respect, beams that employ magnetic fields are more likely to transport FSPs from the interaction region to the detector, with a dependence of σ T upon the magnetic field strength persisting even for weak fields (e.g., ≃4-9 Gauss [11,12]). This type of systematic effect can be reduced by using electrostatic beams which enable both the interaction and detection regions to be field free, thus, facilitating the attainment of a smaller (energy-independent) angular acceptance [25][26][27].…”

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High-Resolution Measurements of e++H2O Total Cross Section

et al. 2016

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Using a purely electrostatic positron beam, the total cross section of positrons scattering from H 2 O has been measured for the first time with a high angular discrimination (≃1°) against forward scattered projectiles. Results are presented in the energy range (10-300) eV. Significant deviations from previous measurements are found which are, if ascribed entirely to the angular acceptances of various experimental systems, in quantitative accord with ab initio theoretical predictions of the differential elastic scattering cross section. DOI: 10.1103/PhysRevLett.117.253401 While the apparent imbalance between matter and antimatter in the Universe remains a major puzzle in science [1,2], much progress in the understanding of the interactions between the two has been achieved through studies of controlled collisions of positrons ðe þ Þ and positronium (Ps, the short-lived atom made of an electron and a positron) with atoms and molecules [3][4][5][6][7].At low energies, the static and polarization interactions tend to cancel for positrons reducing their scattering probability in comparison with electrons. However, polarization often enhances direct ionization by positrons, so that they can be more penetrating and more ionizing than electrons, a result of potential import in analyses of astrophysical (e.g., [8]) and atmospheric events (e.g., [9]) as well as in positron-track simulations for dosimetry in positron emission tomography (e.g., [10]). In turn, these studies contribute to the motivation for investigating the interaction of e þ with water which accounts for about 60% of the human body and which is the most abundant greenhouse gas in the atmosphere.Measurements of positron-water total cross section (σ T ) were first carried out 30 years ago [11,12]. Since then, only a few new results have been added, experimentally [13][14][15] and theoretically [16,17], without a satisfactory agreement emerging among them. The integral (σ el ) and differential (dσ el =dΩ) elastic (el) scattering cross sections for e þ þ H 2 O have also been measured recently [17], complementing theoretical determinations [18,19].Because of the long-range forces involved in the scattering of charged projectiles from a polar molecule such as H 2 O, one of the major difficulties in measuring σ T (even in the case of electrons, e.g., [20][21][22][23]) lies in discriminating against the considerable flux of small forward-angle scattered particles (FSPs) (e.g., [16,19]). The largest error associated with FSPs arises from elastic scattering and rovibrational inelastic processes which cannot be easily distinguished from the incident flux via energy loss discrimination since this is smaller than (or comparable to) typical beam energy resolutions (e.g., the first vibrational excitation from the ground state J ¼ 0 is ≃1595 cm −1 [24]). Detection of FSPs leads to a systematic underestimate of the beam attenuation and, thus, the measured total cross sections. In this respect, beams that employ magnetic fields are more likely to transport FSPs from the...

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