VELOCITY DEPENDENCE OF STABILIZED DOUBLE-ELECTRON CAPTURE IN N7-AR COLLISIONS()

We have studied the two-electron processes in the collision of N7+ wit h argon at various energies. We have measured the radiative stabilizat ion P-rad, defined as the ratio of the true double capture sigma(TDC) to the total double capture which is the sum of sigma(TDC) and the aut oionizing double capture sigma(ADC). A large enhancement of P-rad (17- 44%) with decreasing projectile velocity (0.6-0.14 a.u.) has been foun d. On the other hand, by using the photon-ion coincidence technique to select the double capture processes, we have observed an increase of the emission cross sections of optical transitions from (3, n) Rydberg states with decreasing projectile energy. We give a tentative explana tion which is based on a combination of autotransfer to Rydberg stales and the postcollisional ''satellisation'' of the Rydberg electron des cribed by Roncin and Kazansky.