Angular-dependent electron-capture probabilities for H+in helium, neon and argon

Probabilities for electron capture by 1 H + in helium, neon and argon targets have been measured at projectile energies from 200 to 2500 keV and for laboratory scattering angles from 4 to 130 degrees . A few measurements with 2 H + projectiles are also presented. The angular dependence of the capture probabilities differs in the three targets studied. In helium, the capture probability does not depend on scattering angle, whereas marked variations are seen in both neon and argon. The data are discussed in relation to recent theoretical predictions. A smooth structure seen around a scattering angle of 60 degrees for fast protons on neon is tentatively interpreted in terms of a classical double-scattering mechanism.