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

Electron double differential cross sections for ionization of O2 under fast C6+ ion impact and interference oscillation

The absolute double differential cross sections (DDCS) have been obtained for electron emission from oxygen molecules under the impact of bare carbon ions. The DDCS values are measured between an energy range of a few eV to 600 eV and over an angular range of 30-150°. These are then compared with the continuum distorted wave-eikonal initial state (CDW-EIS)  calculations. The DDCS values for O2 are divided by that of atomic oxygen (calculated theoretically) to look for any oscillatory behaviour arising from Young-type interference. In addition, the DDCS ratios are further divided by a fitted straight line to extract any primary interference oscillation. Although a negative result has been obtained, these observations are in qualitative agreement with the prediction of the CDW-EIS model used.Fil: Nandi, Saikat. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Agnihotri, A. N.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: 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: Martín, F.. Universidad Autónoma de Madrid; España. Instituto Madrileno de Estudios Avanzados en Nanociencia; EspañaFil: Tribedi, Lokesh C.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ