Validity of the continuum approximation in calculating the scattering yields for atom location

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Abstract
The flux distribution of channeled ions has been calculated for 1 MeV He+ in the (100) channel of Cu as a function of the incident angle with the analytical method based on the continuum approximation and the results are compared with those of the Monte Carlo calculations made by Morgan and Van Vliet. General features of the angular dependence of the flux such as the occurrence of the double peak and the incident angles at the maxima agree well in both calculations except for positions along the side of the channel. The scattering yields have been also calculated for atoms located at various positions in the channel. The obtained half-angle of the channeling dip shows a similar temperature dependence as that by Barrett, but the value is larger by 10%. The calculated minimum yield is smaller by a factor of three than that by Barrett. In order to see the discrepancy, the effectiveness factor is calculated on the basis of the continuum approximation and it is found that the effectiveness factor for atoms at the string at the transverse energies near the critical value is substantially smaller than that of the Monte Carlo calculations. However, this discrepancy in the effectiveness factor is found to make little contribution to the scattering yield for the atoms located inside the channel.