Impact ionization of molecular oxygen by 3.5-MeV/u bare carbon ions

We have measured the absolute double-differential cross sections (DDCSs) for electron emission in ionization of O2 molecules under the impact of 3.5-MeV/u C6+ ions. The data were collected between 10 and 600 eV, in an angular range of 30◦ to 150◦. The single-differential cross sections (SDCSs) in emission angle and electron energy are deduced from the electron DDCS spectra. Also, the total cross section has been obtained from the SDCS spectra. The DDCS spectra as well as the SDCS spectra are compared with continuum distorted-wave eikonal initial-state calculations which employ molecular wave functions built as linear combinations of atomic orbitals. The DDCS ratio i.e. σO2/2σO, derived by dividing the experimental DDCS for molecular oxygen with the theoretical DDCS for atomic oxygen, does not show any primary or secondary oscillations arising from Young-type interference, which is apparently in contrast to what has been observed earlier for H2 and in agreement with the model calculation. Similarly, the forward-backward angular asymmetry increases monotonically with the velocity of the emitted electrons. However, the results on the DDCSs, SDCSs, the asymmetry parameter, and the nonexistence of oscillations are in qualitative agreement with the predictions of the model usedOne of the authors (F.M.) acknowledges the financial support from the MICINN Projects No. FIS2010-15127 and No. CSD 2007- 00010. C.A.T., R.D.R., and F.M. acknowledge the Programa de Cooperación Interuniversitaria e Investigación Científica entre España e Iberoamérica AECID Project No. A2/039631/1

Single- and two-centre effects in fully differential cross sections for single ionization of H₂ molecules by 75keV protons

We present theoretical calculations of single ionization of H2 molecules by 75 keV proton impact. The computed fully differential cross sections for different electron ejection geometries and projectile kinematical conditions are compared with recent measurements made by Hasan et al (2014 J. Phys. B: At. Mol. Opt. Phys. 47 215201). We employ a molecular version of the continuum distorted wave-eikonal initial state model, where all the interactions present in the exit channel are considered on an equal footing. In addition, our approach allows us to incorporate different interference terms and to assess their influence. Overall, the agreement between experiment and theory is better than for the case of more sophisticated schemes for coplanar geometries

Single- and two-centre effects in fully differential cross sections for single ionization of H2 molecules by 75keV protons

We present theoretical calculations of single ionization of H2 molecules by 75 keV proton impact. The computed fully differential cross sections for different electron ejection geometries and projectile kinematical conditions are compared with recent measurements made by Hasan et al (2014 J. Phys. B: At. Mol. Opt. Phys. 47 215201). We employ a molecular version of the continuum distorted wave-eikonal initial state model, where all the interactions present in the exit channel are considered on an equal footing. In addition, our approach allows us to incorporate different interference terms and to assess their influence. Overall, the agreement between experiment and theory is better than for the case of more sophisticated schemes for coplanar geometries.Fil: Ciappina, Marcelo Fabián. Institut Max Planck Fuer Quantenoptik; AlemaniaFil: Tachino, Carmen Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Sharma, S.. University Of Missouri; Estados UnidosFil: Schulz, M.. University Of Missouri; Estados Unido

Double-differential cross sections for ionization of H2O by fast bare O ions: Comparison with continuum-distorted-wave eikonal-initial-state calculations in prior and post forms

O vapor in a static gas condition which allowed us to deduce the absolute value of the cross sections. The single-differential cross sections (SDCS) and the total cross sections have also been obtained. The DDCS as well as the SDCS spectra are compared with the continuum-distorted-wave eikonal-initial-state (CDW-EIS) calculations for both the prior as well as the post forms of the scattering matrix. The initial state is represented within the complete neglect of differential overlap approximation, where the molecular orbitals are expressed in terms of atomic orbitals of the atomic constituents. The overall agreement with the CDW-EIS model is quite good as far as the energy dependence is concerned. The prior form of the model is found to provide a better understanding of the data compared to the post version. In particular, excellent agreement between the theory and experiment has been observed for the angular distribution data at forward angles.Fil: Nandi, S.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Biswas, S.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Khan, A.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Monti, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Tachino, Carmen Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Misra, D.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Tribedi, L. C.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ