Unexpectedly large contribution of C5+ deep bound states in C6+ + H collisions

It is demonstrated that ionization and excitation probabilities of a hydrogen atom by C6+ impact are influenced considerably by deep bound states of C5+, which have been disregarded in previous close-coupling calculations because of extremely small transition probabilities. The ionization cross section is overestimated by a few orders of magnitude at 1 keV amu-1 if n = 1 and 2 states of C5+ are not included in the expansion. The same problem is widely inherent in general diabetic-base-expansion treatments of slow collisions if low-lying states are not included fully. (author)