EVIDENCE FOR POPULATION OF HIGHLY ASYMMETRIC STATES IN DOUBLE-ELECTRON CAPTURE BY O(7,8+) AND N(7+) COLLIDING WITH HE AT LOW TO INTERMEDIATE VELOCITIES

Electron capture by O7,8+ and N7+ in collisions with He at 0.2-1.7 a.u . was investigated using coincident recoil momentum spectroscopy. The Q values and angular differential cross sections for single capture, t ransfer ionization (TI), and double capture (DC) were measured. Our Q- value measurements indicate that the electrons are captured into less tightly bound states with increasing collision velocity. The Q values and angular differential cross sections for DC and TI by O8+ are appro ximately the same, while those for DC and TI by O7+ and N7+ differ sig nificantly. Our analysis indicates that the population of very asymmet ric states (n = 2, n' > 10) is necessary to explain this difference.