We report calculations on the total (elastic plus inelastic) positron-scattering cross sections from several diatomic and polyatomic molecules (H&, H20, NH3, CH4, N2, CO, C2H2, O2, SiH4, CO&, N20, and CF4) where experimental data are available. The impact energy (E) range is 10 -5000 eV. A local spherical complex optical potential (SCOP) is calculated for each positron-molecule system from the target charge density [p(r)], which in turn is determined from the corresponding molecular wave function at the Hartree-Fock level. The real part of the SCOP is composed of the repulsive static and attractive positron-correlation-polarization potential of Jain [Phys. Rev. A 39, 2437 (1990)]. The imaginary component of the SCOP, the so-called absorption potential, is derived semiempirically as a function of p(r), E, and the mean excitation energy. The resulting complex optical potential is treated exactly in a variable-phase approach to yield complex phase shift and the total-cross-section quantities. In this intermediateand high-energy region, the small contribution due to the nonspherical nature of the target is neglected. In addition, we fit the total-cross-section values to a simple analytic formula. For molecules possessing a permanent dipole or quadrupole moment, the present results are reliable only roughly above 50 eV. PACS number(s): 34.80.i, 34.90.+ q, 61.80.Fe
The R-matrix method is used to calculate elastic and the excitation cross sections of the six lowest lying electronically excited states of the ClO molecule. These states, of symmetry 1 4 − , A 2 , 1 2 − , 1 2 , 2 4 − and 1 2 + , have vertical excitation energies in the range 3.48 to 6.99 eV. Except for the state A 2 , all other excited states are dissociative. We find a bound state of ClO − with 1 + symmetry with an adiabatic electron affinity of 1.128 eV at an equilibrium bond length of 3.25 a 0 . There are shape resonances of 1 and 3 symmetries at 1.6 and 2.9 eV respectively. Rotationally summed cross sections are obtained for elastic and electronically inelastic scattering for electron-impact energies up to 10 eV.
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