S-WAVE RESONANCES IN POSITRON SCATTERING BY HE+

S-wave e(+)+He+ scattering is calculated using the hyperspherical clos e-coupling method. The two resonances found at about -0.73 Ry and -0.3 9 Ry by Bhatia and Drachman [Phys. Rev. A 42, 5117 (1990)] and reprodu ced by Ho [Phys. Rev. A 53, 3165 (1996)] do not occur in the present r esults. An argument against a these proposed resonances is presented o n the basis of the adiabatic hyperspherical potentials. Instead of the se resonances, we have found narrow Feshbach resonances just below the thresholds (-0.25 a.u. and -0.0625 a.u.) of the formation of Ps(n=1) and Ps(n=2) and an extremely narrow shape resonance just above the thr eshold -0.08 a.u. of He+(n=5). They would be hardly detected since (i) the resonance widths are of the order of 10(-4)-10(-5) a.u. or less, (ii) the resonance is weak in the elastic cross section, (iii) the mag nitudes of the inelastic and Ps-formation cross sections are small, an d (iv) the smooth cross sections due to higher partial waves should st ill be added to the S-wave cross section. [S1050-2947(97)04212-1].