Alicja Domaracka

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.

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 scattering by sulfur tetrafluoride (SF4) molecules

Absolute total cross section (TCS) for electron scattering from sulfur tetrafluoride (SF4) molecules was measured in a linear transmission experiment at energies ranging from low (0.1 eV) to intermediate (370 eV). Below 1.6 eV the TCS function increases steeply towards lower energies and shows small resonant-like maximum near 0.4 eV. Two other distinct enhancements are located at higher energies: a narrow one is peaked at 12 eV, and a very broad hump is centred near 40 eV. Our experimental TCS results are compared with the previous TCS measurements at low impact energies and at intermediate energies—with our total cross section estimations based on calculations of elastic and ionization cross sections. The TCS for SF4 is also compared with SFn (n = 1, 2, 6) total cross sections.

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.

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.

Collisions of electrons with trimethylphosphine [P(CH3)3] molecules

We report on the absolute total electron-trimethylphosphine scattering cross section (TCS) measured from 0.4 to 400 eV using a linear electron-beam attenuation method. The experimental TCS energy function exhibits very pronounced asymmetric enhancement peaked near 5.5 eV. Calculations were also carried out to obtain the integral elastic and ionization cross sections at intermediate and high energies using the independent atom and the binary-encounter-Bethe approximations, respectively. Their sum, the computed total cross section, is for intermediate energies in a reasonable agreement with the present experimental TCS data. Furthermore, the measured TCS for P(CH{sub 3}){sub 3} is compared with the TCSs for some other phosphines [PH{sub 3}, PF{sub 3}] and other methides [B(CD{sub 3}){sub 3}, N(CH{sub 3}){sub 3}]. Analysis clearly shows that exterior atoms of a molecule influence the scattering process more significantly than the central atom.

Electron collision with sulfuryl chloride (SO2Cl2) molecule

Absolute total cross section (TCS) for electron scattering from sulfuryl chloride (SO2Cl2) molecules was measured in a linear transmission experiment at energies ranging from 0.5 to 150 eV. The most distinct features found in the TCS are the deep minimum located near 1.8 eV and the broad enhancement peaked around 9.5 eV with a shoulder spanned between 3 and 5 eV. At intermediate energies, the present experimental TCS results agree well with our total cross-section estimations, based on calculations of elastic and ionization cross sections. In addition, the calculated total cross section for SO2F2 is reported. The results for e−–SO2Cl2 collisions are compared, for the energy dependence and magnitude, with experimental and computed cross sections for other molecules (SO2F2, SO2ClF) comprising a sulfone group.

Collisions of electrons with trimethylamineN(CH3)3molecules

Absolute total electron-trimethylamine scattering cross section (TCS) has been measured from

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

0.8\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}370\phantom{\rule{0.3em}{0ex}}\mathrm{eV}

Cross sections calculations for electron scattering from dimethylamine, NH(CH3)2, molecule

with a linear electron-transmission method. The experimental TCS energy function is dominated by very pronounced enhancement peaked near