Kunizo Onda

Model potentials for electron scattering - Converged close coupling calculations for the differential cross section for e/-/N2 at 30-50 eV

We have calculated the elastic scattering and rotational excitation cross sections for e−–N2 scattering at 30 and 50 eV using quantum chemical techniques specially designed to be applicable to elastic and inelastic electron scattering by general polyatomic molecules. The angle dependence of the sum of the elastic and rotational excitation differential cross sections is in good agreement with experiment at all scattering angles at both energies, but at 50 eV the difference from experiment exceeds the experimental uncertainty at small scattering angles and near the minimum of the differential cross section. At large scattering angles the rotational excitation cross sections are predicted to exceed the elastic scattering cross sections. The absolute cross sections agree with experiment at some angles but at other angles are as much as 51% (30 eV or 90% (50 eV) higher; this may be due at least in part to the difficulty of putting the experimental results on an absolute scale.

SCF treatment of charge polarization effects in intermediate-energy electron scattering calculations with applications to N2

We report converged rotational close coupling calculations of the differential, integral, and momentum‐transfer cross sections for seven model potentials for electron–N2 scattering at an impact energy of 30 eV. The model potentials involve a static potential calculated by the INDO/1s or INDOXI/1s method, an exchange potential calculated by the semiclassical exchange approximation from the INDO/1s or INDOXI/1s unperturbed electronic density, and a polarization potential. The polarization potentials used include the Buckley–Burke semiempirical one and various modifications of the INDOXI and INDO self‐consistent‐field adiabatic polarization potentials. We are able, without adjusting parameters, to obtain good agreement with the angle dependence of the experimentally measured sum of the elastic and rotational excitation differential cross sections although the absolute value of our calculated cross sections is about 20%–30% larger than the measured values in the best case, perhaps indicating that the model po...

State‐to‐state cross sections for electron impact on N2. Close coupling and polarized Born calculations for rotational and vibrational excitation and pure elastic scattering at nonresonant energies

Calculations of cross sections for elastic scattering, rotational excitation, and vibrational excitation of ground state N2 by electrons with impact energies of 10 and 50 eV have been performed using realistic static‐exchange‐plus‐polarization interaction potentials, rotational close coupling, and the vibrational sudden approximation. The effect of vibrational averaging on the elastic scattering is found to be small. The calculated integral cross sections for pure elastic scattering and for pure rotational (summed over j′≠0), pure vibrational (j′=0,v’=1 and 2), and mixed rotational–vibrational (summed over j′≠0 for v′=1 and 2) excitation are 34.4, 18.6, 2.70×10−2, and 4.13×10−2 a02, respectively, at 10 eV and 19.4, 11.7, 1.28×10−2, and 6.92×10−2 a02, respectively, at 50 eV. The sum of the differential cross sections for pure vibrational and mixed rotational–vibrational excitation for v=0→v′=1 can be compared to experiment and agreement is good at both energies except for scattering angles ϑ?30°. The pure ...

Electron–molecule scattering at intermediate energy. Centrifugal‐dominant channel decoupling and the INDOX polarized SCF model applied to N2 at 50 eV

We have calculated cross sections for vibrationally–electronically elastic electron−N2 scattering at 50 eV impact energy. The model interaction potential includes static, exchange, and polarization interactions calculated by the INDOX/1s method and the semiclassical exchange approximation with adiabatic polarization at large electron–molecule distances. The scattering is treated by converged rotational close coupling using a new channel decoupling scheme.

Comparison of local‐exchange approximations for intermediate‐energy electron–molecule differential cross sections

Converged rigid‐rotator rotational close coupling calculations have been performed for two different effective potentials. The differential cross sections for intermediate energy electron–molecule scattering are calculated. (AIP)

Close-coupling calculations with an INDOX/1s static potential, semiclassical exchange, and a semi-empirical polarisation potential for electron-CO2 elastic scattering and rotational excitation

A semi-empirical molecular-orbital method for modelling the effective potential for electron-molecule scattering is applied to elastic scattering and rotational excitation of CO2 at 20 eV impact energy. Agreement with experiment is reasonably good. The calculated rotationally summed integral cross section is 67.8 a02.

State‐to‐state cross sections for elastic and inelastic electron scattering by N2 at 20–35 eV, including resonant enhancement of vibrational excitation

We have calculated integral and differential cross sections for elastic scattering and rotational, vibrational, and rotational‐vibrational excitation at 20, 25, and 30 eV. We have also calculated partial cross sections and eigenphase sums at these energies and at 35 eV. We present a detailed study of the resonance enchancement of the vibrational excitation cross section in this energy region.

Electron scattering by CO2: Elastic scattering, rotational excitation, and excitation of the asymmetric stretch at 10 eV impact energy

Coupled‐channels calculations based on an effective potential are presented for electron scattering by CO2 at 10 eV impact energy. The processes studied are pure elastic scattering, rotational excitation, and vibrational excitation of the asymmetric stretch; the vibrational excitation is always accompanied by rotational excitation. The quantities calculated are differential, partial, integral, and momentum transfer cross sections, both state to state and summed over final rotational states for a given final vibrational level. The effective potential is based on the INDOX2/1s method for the static and polarization potentials and the semiclassical exchange approximation for the exchange potential. There are no empirical parameters. The present calculations are compared to experiment and to previous calculations where available, and we also perform calculations with an altered polarization potential to further elucidate the reasons for the differences from one of the previous calculations. The agreement of t...

Quantum mechanical study of elastic scattering and rotational excitation of CO by electrons

We report close coupling calculations of differential, integral, and momentum transfer cross sections for pure elastic scattering and rotational excitation of CO by electron impact. The calculations are based on a static charge distribution that has correct dipole and quadrupole moments, has cusps at the nuclei, and is augmented by an SCF treatment of charge polarization and a local approximation for exchange. The rotationally summed cross sections, with no adjustable parameters in the scattering calculation, are in reasonably good agreement with the experimental cross sections but are somewhat larger at small scattering angles. The state‐to‐state differential cross sections show several interesting features, including very large contributions to small‐angle scattering from large angular momenta and a ’’propensity rule’’ favoring even Δj over odd Δj at almost all scattering angles for Δj≲4 where Δj is the change in rotational quantum number.

Elastic scattering and rotational excitation of a polyatomic molecule by electron impact: Acetylene

We have calculated differential, integral, momentum transfer, and partial cross sections for elastic scattering and rotational excitation of C2H2 by 10 eV electrons. The effective potential includes static, exchange, and polarization interactions calculated by the INDOX/1s method and the semiclassical exchange approximation with adiabatic polarization at large electron–molecule distances. The scattering is treated by well converged rotational close coupling using the centrifugal dominant scheme to select the channels included and including up to 32 coupled channels for a given total angular momentum. The calculated integral cross sections for pure elastic scattering and rotational excitation are 54.5 and 41.4a02 , respectively. These are much larger than the values (34.4 and 18.6a02) previously [K. Onda and D. G. Truhlar, J. Chem. Phys. 71, 5107 (1979)] calculated for the isoelectronic molecule N2 at this energy. This illustrates how the greater spatial extent of C2H2 greatly increases the cross sections ...