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In this work, we report theoretical electron capture cross sections for single-electron removal from molecules of biological interest and noble gases by bare ion (H + and H e 2+) impact at energies ranging from 25 to 10,000 keV/amu. We use a distorted wave (DW) method where the intermediate continuum state of the active electron with the target ion has been taken into account. This method is developed within the framework of the independent electron model taking particular care of the representation of the bound continuum target states. Two different approximations have been considered for molecular targets: molecular representation of the bound-state target wavefunction and Bragg's additivity rule. The molecular orbital for targets are described within the framework of the complete neglect of differential overlap (CNDO) method based on the linear combination of atomic orbital (LCAO) approximation. Using the DW method, we have also calculated the K-, Land M-shell electron capture in collisions of bare ions with three noble gases He, Ne, and Ar respectively. Contributions from different molecular orbitals and different shells to the total cross sections (TCS) are studied. The preference of electron capture occurs in accordance as the binding energy of the active electron in molecular orbital and atomic shell. The maximum contributions to TCS for SC comes from the less bound electrons in repetitive orbitals, whereas the tightly bound electrons dominate the TCS at higher projectile energy regime. Variation of TCS with impact energy are compared with the available experimental observation and other theoretical findings. We find that the present theoretical method is satisfactory in both intermediate and high-energy region for molecules as well as noble gas targets to give reliable outcomes compared to other theoretical methods.

The differential and total cross sections for both single and double electron capture in collisions of +H and He 2+ with ground state helium atom have been studied by means of the four-body model of target continuum distorted wave (TCDW-4B) approximation in the energy range from 30 to 1000 keV amu -1 . In this model, distortion in the final channel related to the Coulomb continuum states of the active electron(s) in the field of residual target ion are included. The calculations are based on the independent electron model. The present computed results are compared with the available experimental and other theoretical results. Total cross sections are found to be in good agreement with the measurements. We have also analysed differential cross sections (DCS) for both single and double electron capture in the collision of proton and αparticles with helium atoms at different projectile energies. The present DCS data exhibits the typical steeply decreasing dependence on the projectile scattering angles, but neither oscillating structures characteristic of interference effects nor peaks reminiscent of the Thomas peak are observed at different projectile energies. The obtained results for the DCS into the ground state are compared with the experimental data and overall a satisfactory agreement has been found. Finally we have also studied the variation of double to single capture differential cross-section ratios with projectile scattering angles at different impact energies.

Within the framework of independent electron approach, the prior form of boundary corrected continuum intermediate state (BCCIS) approximation is employed to calculate the cross sections for total single electron capture in collision of bare ions (H + , He 2+ and Li 3+ ) with biological molecules in the intermediate to high energy regimes. With a suitable choice of the distorting potential, the boundary condition is satisfied with a proper account of the intermediate continuum states. The cross sections have been calculated from 25 keV/amu to 10 MeV/amu. We have approximated the cross sections for molecular targets by the linear combination of atomic cross sections weighted by the effective occupation electron number. Furthermore, the multi-electronic problem is reduced to a mono-electronic one using a version of the independent electron approximation. A detailed analysis on the contributions from different molecular orbitals to total cross sections is reported. In the present investigation, we observe clearly the importance of the core contribution in the change of slope of the TCS curves. Moreover, analysis has been made on the cross section per target electron resulting in achievement of a 'universal' cross section. However, some negligible discrepancies are observed for the case of the CH 4 molecule. The present computed results in prior from of BCCIS method have been compared with the available theoretical and experimental results. We found that our computed results are in good agreement with the experimental findings.