Positron impact scattering cross-sections for pyridine and pyrimidine are reported here. Spherical complex optical potential formalism is used to calculate the positronium formation, elastic, total, and differential cross-sections. The ionization cross-sections calculated here are obtained employing the complex scattering potentialionization contribution method. To account for the complex molecular structure of the target, an effective potential method is employed in our formalism for the first time. The contribution from rotational excitation is also included, which shows a reasonable comparison with the experimental data. The results obtained using the modified approach are encouraging and show very good agreement with the measurements. The differential cross-section for pyridine is reported for the first time.

In the present work, a detailed study on the electron impact excitation of Xe7+, Xe8+, Xe9+ and Xe10+ ions for the reddipole allowed (E1) transitions in the EUV range of 8–19 nm is presented. The multi-configuration Dirac–Fock method is used for the atomic structure calculation including the Breit and QED corrections along with the relativistic configuration interaction approach. We have compared our calculated energy levels, wavelengths and transition rates with other reported experimental and theoretical results. Further, the relativistic distorted wave method is used to calculate the cross sections from the excitation threshold to 3000 eV electron energy. For plasma physics applications, we have reported the fitting parameters of these cross sections using two different formulae for low and high energy ranges. The rate coefficients are also obtained using our calculated cross sections and considering the Maxwellian electron energy distribution function in the electron temperature range from 5 eV to 100 eV.

Synopsis Advancement in medical technology is a much needed demand in the present scenario. To stem a robust technology, one should be aware of the knowledge behind such sciences. In view of this, we investigate here the interaction of biomolecules with the most elementary particle, electron along with its anti-particle positron. The cross sections computed here using SCOP formalism for pyridine molecule will be useful for simulations of bio molecular systems. We further compare the cross sections for e− and e+ scattering extracting some rudimentary information about these basic interactions.

Results of experimental and theoretical investigations of electron-impact excitation of the resonance 6s6p (_ ^1)P_1^°  6s2 1S0 (132.2 nm) as well as the cascade 6s7s 1S0  6s6p (_ ^1)P_1^° (309.2 nm) and 6p2 1D2  6s6p (_ ^1)P_1^° (150.8 nm) spectral transitions from the ground 6s2 1S0 level in the thallium ion are presented. Crossed beams of electrons and Tl+ ions in combination with a spectroscopic method were used in the experiment. Measured cross-sections have a distinct resonance structure arising mainly from the electron decay of atomic 5d96s26p2, 5d106s7s(1S)np (n≥7), 5d106s6d(1D)np (n≥6), 5d106s6d(1D)nd (n≥6) and ionic 5d96s2np, 5d96s2nd, 5d96snp (n6) autoionizing levels as well as radiative transitions from the higher 6s7s 1S0, 6s6d 1D2, and 6p2 1D2, 1S0 ionic levels. Relativistic distorted wave (RDW) calculations are performed to obtain the effective cross-sections for the above transitions. The absolute values of the cross-sections are found to be 1.3910–16 cm2 at 300 eV for the 132.2 nm resonance line, 0.1110–16 cm2 and 0.5610–16 cm2 at 100 eV for the 309.2 nm and 150.8 nm lines, respectively. The contribution of the cascade transitions under study to the effective cross section of the 132.2 nm resonance line at the energy of 100 eV is about 30%. Calculation using the semi-empirical Van Regemorter formula is also performed to obtain the effective cross-section of the resonance 132.2 nm line. The absolute value of the cross-section at 300 eV is found to be nearly the same as given by the RDW calculation.

The results of experimental and theoretical studies on electron-impact excitation of the 6s6p P 31°→6s2 S 10 (λ190.8 nm) and 6s7s S 10→6s6p P 31°  (λ179.9 nm) intercombination transitions in the single-charged thallium ion are presented. The crossed-beams technique was used in combination with a spectroscopic method in the experiment. A distinct structure was revealed in the cross-sections of both lines results from electron decay of atomic autoionizing states and radiative transitions from upper ionic levels. The dominant mechanism of the structure formation was the Coster–Kronig process. Relativistic distorted wave calculations were performed to obtain emission cross-sections for the above transitions. The absolute values of the cross-sections were found to be (0.25 ± 0.08) × 10−16 cm2 (λ190.8 nm) and (0.10 ± 0.04) × 10−16 cm2 (λ179.9 nm) at the electron energy of 100 eV.