Ionisation of He atoms by H+, He2+and Li3+nuclei

The cross sections, sigma i1 and sigma i2, of single and double ionisation of He atoms by H+, He2+, and Li3+ nuclei with energies ranging from 0.01 to 5 MeV amu-1 are calculated in the independent-electron approximation. The calculations are made for three versions of the probabilities of one-electron transitions to the continuum. The double ionisation of He by nuclei with energies E/A approximately 0.1-Z2 meV amu-1 is mainly due to the independent interaction of each atomic electron with the bombarding nucleus. The values of sigma i1 for all nuclei with E/A>or=0.2MeV amu-1 and of sigma i2 for He2+ and Li3+ nuclei with E/A=0.2-0.5 MeV amu-1 calculated in one of the versions are found to agree with the experimental values. The calculated values of sigma i2 for protons with E=0.2-0.7 MeV and 1.5-4 MeV are respectively higher and lower than the experimental values because the authors calculations were made neglecting the electron correlations.