Total Cross Section Energy Research Articles

Role of methylation in electron scattering on X(CH3)4 (X= C, Si, Ge) molecules

To investigate how replacement of H atom with methyl group (CH3) – in tetrahedral compounds of carbon, silicon and germanium – affects electron scattering process, total cross sections (TCS) for electron scattering from C(CH3)4, Si(CH3)4 and Ge(CH3)4 molecules have been compared with data for CH4, SiH4 and GeH4 molecules. All examined data have been obtained with the same experimental setup. The shape of all discussed TCS energy dependences is very similar and is characterized by a dominant maximum peaked below 10 eV. For methylated compounds a gentle structure is also visible on high energy slope of main enhancement, between 10 – 20 eV. A simple formula for TCS evaluation for partially methylated carbon, silicon and germanium compounds is also proposed.

Cross sections for electron collision with pyridine [C5H5N] molecule

ABSTRACTThe absolute grand -total cross section (TCS) for electron scattering from pyridine, C5H5N, molecules has been measured at impact energies from 0.6 to 300 eV in the linear electron-transmission experiment. The obtained TCS energy dependence appears to be typical for targets of high electric-dipole moment; the cross section generally decreases with rising energy, except for the 3–20 eV range, where a broad enhancement peaked near 8.5 eV is clearly visible. Below 10 eV, some weak structures which can be attributed to resonant scattering processes are also discernible. The present TCS energy dependence is compared with TCS experimental data reported very recently. Comparison with TCS for benzene is also made to search how the replacement of the CH group in the benzene ring with the nitrogen atom influences the electron-scattering process. In addition, for pyridine and its halogenated derivatives: 2-chloropyridine [2-CHClN] and 2-bromopyridine [2-CHBrN], integral elastic (ECS) and ionisation (ICS) cross sections have been calculated at intermediate and high electron-impact energies within semiempirical approaches. For pyridine the sum of ECS and ICS is in reasonable agreement with the measured TCS above 40 eV.

Total Ambient Dose Equivalent Buildup Factor Determination for Nbs04 Concrete.

Buildup factors are dimensionless multiplicative factors required by the point kernel method to account for scattered radiation through a shielding material. The accuracy of the point kernel method is strongly affected by the correspondence of analyzed parameters to experimental configurations, which is attempted to be simplified here. The point kernel method has not been found to have widespread practical use for neutron shielding calculations due to the complex neutron transport behavior through shielding materials (i.e. the variety of interaction mechanisms that neutrons may undergo while traversing the shield) as well as non-linear neutron total cross section energy dependence. In this work, total ambient dose buildup factors for NBS04 concrete are calculated in terms of neutron and secondary gamma ray transmission factors. The neutron and secondary gamma ray transmission factors are calculated using MCNP6™ code with updated cross sections. Both transmission factors and buildup factors are given in a tabulated form. Practical use of neutron transmission and buildup factors warrants rigorously calculated results with all associated uncertainties. In this work, sensitivity analysis of neutron transmission factors and total buildup factors with varying water content has been conducted. The analysis showed significant impact of varying water content in concrete on both neutron transmission factors and total buildup factors. Finally, support vector regression, a machine learning technique, has been engaged to make a model based on the calculated data for calculation of the buildup factors. The developed model can predict most of the data with 20% relative error.

Electron scattering from 2-methyl–1,3-butadiene,C5H8, molecules: Role of methylation

We report cross-section results from experimental and theoretical investigations into electron collisions with the 2-methyl\char21{}1,3-butadiene $[{\mathrm{C}}_{5}{\mathrm{H}}_{8}]$ molecule. The current results are compared with our previous results for the 1,3-butadiene $[{\mathrm{C}}_{4}{\mathrm{H}}_{6}]$ molecule, a structural homologue of 2-methyl\char21{}1,3-butadiene, to investigate how the methylation (the substitution of hydrogen atom by a methyl group) affects the shape and/or magnitude of the total cross sections (TCSs). Both experimental TCS energy dependencies have certain features in common: the Ramsauer\char21{}Townsend-like minimum located within 1.4\char21{}1.6 eV; the resonant maximum centered at 3.4 eV for the 2-methyl\char21{}1,3-butadiene molecule and at 3.2 eV for 1,3-butadiene; a weak shoulder in the vicinity of 7 eV; and the pronounced broad enhancement peaking around 8.5 eV for 2-methyl\char21{}1,3-butadiene and near 9.5 eV for 1,3-butadiene. The magnitude of the TCS for 2-methyl\char21{}1,3-butadiene appears to be higher than that for 1,3-butadiene over the whole investigated energy range. Closer analysis of data shows that the TCS for 2-methyl\char21{}1,3-butadiene can be reasonably reproduced by the sum of TCSs for 1,3-butadiene and half of the TCS for the ethane $[{\mathrm{C}}_{2}{\mathrm{H}}_{6}]$ molecule\char22{}that stays for the TCS of the methyl unit $[{\mathrm{CH}}_{3}]$. That result can be extended to homologous series of methyl-substituted allenes, ethylenes, and acetylenes.

Scattering of electrons from 1-butene, H2C=CHCH2CH3, and 2-methylpropene, H2C=C(CH3)2, molecules

We report absolute grand total cross sections (TCSs) for electron scattering from 1-butene (H2C=CHCH2CH3) and 2-methylpropene (H2C=C(CH3)2) molecules, measured at electron impact energies ranging from 1 to 400 eV and from 1 to 350 eV, respectively, using a linear electron-transmission technique. The general shape of cross sections for both butene isomers looks similar. Two structures in each TCS energy curve are discernible: a small peak in the vicinity of 2.3 eV and a pronounced very broad enhancement with the maximum located around 8 eV. The magnitude of TCS for 2-methylpropene appears somewhat higher than that for 1-butene below 20 eV, while above 70 eV the TCS curves practically overlap. In addition, comparison is made of TCSs for an ethylene (H2C=CH2) molecule and its mono and double methyl-substituted derivatives: propene (H2C=CHCH3) and 2-methylpropene.

Cross sections for electron collision with five-membered ring heterocycles

The absolute total cross-section (TCS) for electron scattering from isoxasole, (CH)3NO, molecule has been measured using the linear transmission technique for impact energies ranging from 1 to 400 eV. The measured TCS energy dependence appears typical for highly polar targets; over whole energy range applied, the magnitude of TCS generally decreases as the energy increases. Some narrow features located near 1.2 and 2.7 eV have been observed in the TCS curve as well as a broad enhancement spanned between 5 and 15 eV. The TCS for electron-isoxazole scattering has been compared with TCS data for furan, (CH)4O; differences and similarities in the appearance of both TCSs energy functions are indicated and discussed. In addition, for several five-membered ring heterocycle molecules: isoxazole, pyrrole [(CH)4NH] and tiophene [(CH)4S], integral elastic (ECS) and ionization (ICS) cross sections have been calculated at intermediate and high electron-impact energies in the additivity rule approximation and the binary-encounter-Bethe approach, respectively. For isoxazole and furan the sums of ECS and ICS are in very good agreement with the respective measured TCSs above 50 − 60 eV.

Electron scattering from hexafluoroacetone molecules: cross section measurements and calculations

Absolute total cross section (TCS) for electron scattering from hexafluoroacetone (HFA: (CF3)2CO) molecules has been measured from 1 to 400 eV, employing a linear electron-transmission technique. The TCS energy function for the electron–HFA collision has two broad enhancements: the first, visible between 2 and 28 eV, can be partly attributed to resonant processes; the second is much broader, centred around 50 eV, and is characteristic of perfluorinated targets. The low-energy enhancement is superimposed with weak features perceptible near 3.6, 8.5 and 17 eV. Calculations were carried out for HFA and for acetone to obtain the integral elastic and ionization cross sections at intermediate and high incident energies, using the independent atom approximation and binary-encounter-Bethe approach, respectively. The computed total (elastic plus ionization) cross sections are above 70 eV in reasonable agreement with the experimental TCSs. A comparison is made between cross sections for HFA and its per-hydrogenated counterpart, acetone ((CH3)2CO); the effect of perfluorination is indicated.

Total electron-scattering cross section measurements for tetrahydropyran, (CH2)5O, molecules

Absolute total cross section (TCS) for electron scattering from tetrahydropyran (THP: (CH2)5O) molecules has been measured from 1 to 400 eV, using a linear electron transmission technique. The TCS energy function for electron–THP collisions is characterized by the broad enhancement spanned between 3 and 15 eV, which can be attributed to resonant processes. Comparison is also made between the present results for THP and earlier TCS measurements for tetrahydrofuran (THF: (CH2)4O) and α-tetrahydrofurfuryl alcohol (THFA: C5H10O2).

Cross sections for electron scattering from furan molecules: Measurements and calculations

Electron-scattering cross sections have been determined for the furan (C${}_{4}$H${}_{4}$O) molecule, both experimentally and theoretically. An absolute total cross section (TCS) has been measured over energies from 0.6 to 400 eV using a linear electron-transmission method. The TCS energy function is dominated with a very broad enhancement, between 1.2 and 9 eV; on the low-energy side, some resonant structures are visible. Integral elastic (ECS) and ionization (ICS) cross sections have been also calculated up to 4 keV in the additivity rule approximation and the binary-encounter-Bethe approach, respectively. Their sum, ECS$+$ICS, is in a very good agreement with the measured TCS above 70 eV.

Scattering of electrons from acetaldehyde and acetone

Absolute total cross sections (TCSs) for electron scattering from acetaldehyde [(CH3)CHO] and acetone [(CH3)2CO] molecules have been measured at electron-impact energy extending from 0.7 to 400 eV, using a linear electron-transmission technique. The shape of obtained TCS energy dependences appears typical for targets of high electric dipole moment; both TCSs decrease with the energy increase; only between 4 and 12 eV is a weak enhancement in TCSs is clearly perceptible. The experimental TCSs for (CH3)CHO and for (CH3)2CO are also compared with those for their cyclic isomeric counterparts: c-(CH2)2O and c-(CH2)3O, respectively.

Electron scattering by trimethylene oxide, c-(CH2)3O, molecules

Electron-scattering cross sections have been determined for trimethylene oxide, cyclic (CH(2))(3)O molecule, both experimentally and theoretically. The absolute total cross section (TCS) has been measured over energies from 1 to 400 eV using a linear electron-transmission method. The obtained TCS generally decreases with rising energy, except for the 3-10 eV range, where some resonantlike structures are discernible. Integral elastic cross section (ECS) and ionization cross section (ICS) have been also calculated up to 3 keV in the additivity rule approximation and the binary-encounter-Bethe approach, respectively. Their sum, ECS+ICS, is in a good agreement with the measured TCS. Comparison of the TCS energy dependence for trimethylene oxide with that for its isomeric open-chain counterpart--acetone, (CH(3))(2)CO, has also been made. Moreover, examination of experimental TCSs for the cyclic (CH(2))(n)O, n=2-4, ether series reveals that the intermediate-energy molecular TCSs for members of that family can be nicely represented as a sum of the effective TCSs for particular constituents of the molecule, i.e., methylene groups and oxygen atom. Finally, based on these partial TCSs, the TCS for the c-(CH(2))(5)O--the next member of the series--has been determined and compared with the respective ECS+ICS values computed here for this compound.

Electron collisions with ethylene oxide molecules

The absolute total cross section (TCS) for electron–ethylene oxide (c-C2H4O) collisions was measured at electron-impact energies extending from 0.7 to 400 eV using the linear electron-transmission technique. In the present TCS energy function a distinct peak is visible near 4.6 eV which may be attributed to formation of a short-lived negative ion. Moreover, at intermediate and high energies the integral elastic (ECS) and ionization (ICS) cross sections were determined numerically. The calculated sum, ECS + ICS, is in good agreement with the experimental TCS in the overlapping energy range. Finally, the present experimental TCS for electron scattering from c-C2H4O is compared with that for its cyclic isoelectronic counterpart c-C3H6, and similarities and differences are pointed out and discussed.

Electron collision with B(CD3)3 molecules

Absolute total cross section (TCS) for electron–trimethylborane-d9 (B(CD3)3, TMB-d9) collisions has been measured at energies ranging from 0.4 to 370 eV using the linear electron-transmission technique. The most visible feature of the TCS energy function is a pronounced broad enhancement peaked between 5 and 10 eV. Some weak structures are also perceptible in the TCS curve. At intermediate energies the experimental results are compared with the cross section obtained as a sum of the integral elastic and ionization cross sections calculated in this work for the B(CH3)3 molecule. Similarities observed in cross sections for planar, boron-containing BX3 (X = F, Cl, CD3) molecules are also pointed out and discussed.

Cross sections for electron scattering from sulfuryl chloride fluoride (SO2ClF) molecules

Absolute total cross section (TCS) for electron scattering from sulfuryl chloride fluoride (SO2ClF) molecules was measured in a linear transmission experiment at energies ranging from 0.6 to 370 eV. The experimental TCS energy function has a deep minimum (30 × 10−20 m2) at 3 eV which separates two distinct TCS enhancements. Below 3 eV the TCS curve increases steeply towards lower energies with a small resonant maximum visible near 2.2 eV. Above 3 eV the TCS is dominated by second pronounced enhancement with the maximum (45 × 10−20 m2) peaked near 9.5 eV. The experimental TCS findings are—at intermediate energies—satisfactorily reproduced with our total cross section estimation based on calculations of integral elastic (in independent atom approximation) and ionization (binary-encounter-Bethe approach) cross sections. The TCS measured for SO2ClF is also compared with experimental TCSs for molecules containing sulfur as a central atom and it is found that some features observed for SO2ClF are shared by others of the compared molecules.

Electron collisions with boron trichloride(BCl3)molecules

Absolute total cross section (TCS) for electron scattering by boron trichloride $(\mathrm{B}{\mathrm{Cl}}_{3})$ molecules has been measured in a linear transmission method under single collision conditions. Measurements have been performed within electron energy range from 0.3 to 370 eV. The TCS energy function for $\mathrm{B}{\mathrm{Cl}}_{3}$ is dominated with very pronounced enhancement peaked near 10 eV ($61\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\phantom{\rule{0.3em}{0ex}}{\mathrm{m}}^{2}$ in the maximum). Low-energy slope of the enhancement is superimposed with two resonantlike structures located near 3.2 and 6.0 eV. On the descending high-energy side of the TCS curve only a weak shoulder between 30 and 60 eV is discernible. The present TCS is compared with the existing experimental and calculated cross sections for particular ${e}^{\ensuremath{-}}\text{\ensuremath{-}}\mathrm{B}{\mathrm{Cl}}_{3}$ scattering processes. Furthermore, the TCS for $\mathrm{B}{\mathrm{Cl}}_{3}$ is also confronted with the TCS for $\mathrm{B}{\mathrm{F}}_{3}$ and the role of peripheral atoms in molecule is indicated and discussed.

Electron collisions with trifluorides: BF3 and PF3 molecules.

Absolute total cross sections (TCSs) for electron scattering from boron trifluoride (BF(3)) and phosphorus trifluoride (PF(3)) molecules have been measured using a linear transmission method. The electron energy ranges from 0.6 to 370 eV for BF(3) and from 0.5 to 370 eV for PF(3). The TCS energy dependence for BF(3) exhibits two very pronounced enhancements: resonantlike narrow feature located near 3.6 eV with the maximum value of 19.2 x 10(-20) m(2), and intermediate energy very broad enhancement with two humps, one centered around 21 eV (18.8 x 10(-20) m(2) in the maximum) and the other near 45 eV (19.5 x 10(-20) m(2)). For PF(3) the TCS has quite different low-energy dependence: at 0.5 eV it has a high value of 70 x 10(-20) m(2) and decreases steeply towards higher energies. Beyond the minimum near 5.5 eV, the TCS reveals two distinct humps: the resonant one centered near 11 eV with the peak value of 32.9 x 10(-20) m(2) and the second one much broader around 35 eV (27.9 x 10(-20) m(2)). The present TCSs for trifluorides are compared to each other as well as to previous TCS data for selected perfluorides and to results for their perhydrided counterparts. The differences and similarities in the shape and magnitude of TCSs are pointed out.

Scattering of electrons from hydride molecules: PH3

An absolute total cross section (TCS) for electron scattering from phosphine (PH3) molecules was obtained in a linear transmission experiment at energies ranging from low (0.5 eV) to intermediate (370 eV). The dominant behaviour of the TCS energy function is a very pronounced low-energy enhancement with two distinct resonant-like humps peaked at around 2.4 and 6 eV. Above 10 eV the TCS is a rather featureless, monotonically decreasing function of energy. Our experimental results are compared with the theoretical predictions and intermediate-energy measurements. The similarities and differences of experimental TCS data for isoelectronic hydrides containing third-period atoms (SiH4, PH3, H2S and HCl) are also pointed out and discussed.

Isomer effects on the total cross section for electron scattering fromC4F6 molecules

The absolute total cross section (TCS) for electron scattering from hexafluoro-1,3-butadiene(1,3-C4F6) was obtained in a transmission experiment for electron impact energies from0.6 to 370 eV. The TCS energy function has two pronounced enhancementsseparated by a deep minimum located near 2.6 eV: a low-energy hump around1 eV and a dominant very broad enhancement centred near 30 eV. The1,3-C4F6 TCS results are compared with the data for hexafluoro-2-butyne(2-C4F6) and the influence of the structural differences on the electron-scattering TCS for isomers of theC4F6 molecule (isomeric effect) is explicitly indicated. The most pronounced role of the moleculargeometry on the magnitude and shape of the TCS energy dependence is observed atthe lowest energies studied. Above 40 eV the TCSs for both isomers are closeto each other. Some conformities of TCSs within a series of perfluorocarbons(C2F4,1,3-C4F6, C6F6) as well as in a series of their hydrocarbon counterparts(C2H4,1,3-C4H6, C6H6) are also pointed out and discussed.

Electron collisions with tetrafluoroethylene(C2F4)and ethylene(C2H4)molecules

Absolute total cross sections (TCSs) for 0.6-370 eV electrons scattered by tetrafluoroethylene (C{sub 2}F{sub 4}) molecules have been measured using a linear transmission method. The TCS energy function for C{sub 2}F{sub 4} shows one very broad enhancement with the maximum value of 30x10{sup -20} m{sup 2} located around 30 eV. On the low-energy slope of the TCS curve some weak features near 2.8, 9.5, and 16 eV are discernible. Above 50 eV the present TCS agrees well with theoretical predictions. Absolute TCS for ethylene (C{sub 2}H{sub 4}) has also been measured and compared with the TCS for C{sub 2}F{sub 4}. Effect of substitution of fluorine atoms for hydrogen (perfluorination effect) was indicated and discussed. The reported TCS for C{sub 2}H{sub 4} is distinctly higher than experimental data existing so far.

Electron scattering from C4H6 andC4F6molecules

Absolute electron-impact total cross sections (TCSs) for C4H6isomers (1, 3-butadiene and 2-butyne) and for hexafluoro-2-butyne (C4F6)have been measured in a linear electron-beam transmission experiment as afunction of impact energy, between 0.5 and 370 eV. For the C4H6molecule distinct differences in the shape and magnitude of TCS energydependences of both isomers are apparent at low energies. In the 1, 3-butadieneTCS curve, the enhancement below 1.2 eV, the narrow maximum centred around3.2 eV and the dominant broad peak at 9–9.5 eV are easily distinguishable; a veryweak shoulder is located near 8 eV. The TCS energy function of 2-butynedemonstrates a remarkable resonant-like maximum located near 3.6 eV andmuch broader enhancement centred at 8 eV. Above 50 eV both C4H6curves merge together. The hexafluoro-2-butyne TCS has the maximum near 8 eVand very broad enhancement spanning between 20 and 80 eV; weak shouldersnear 3 and 6 eV are also noticeable. The effect of perfluorination is indicated.