Are some rydberg states formed by post-target electron capture?

Abstract

Studies of L X-rays emitted downstream from foil-excited beams of 130 MeV Br ions show a rich distribution of Rydberg states. These arise from three distinct populations, namely a statistical distribution of high (~63%) intensity, an s-wave population of low (~2.38%) intensity and a continuously-fed population which appears to be replenished in flight. Of these, the first appears to be created in ions initially excited in-target by an unknown mechanism that transmits high angular momentum, while the third is completely mysterious. The second population, of high principal quantum number n (~40–100), is a candidate for a creation mechanism involving capture post-target of convoy electrons formed by projectile ionisation. A calculation has been made of the expected probability of this process occurring, and by means of a Monte Carlo simulation this mechanism is shown to be consistent with the observed data. It is a condition of the model that the convoy electrons, prior to emerging from the target, have remained close to their host ions. This picture is discussed in relation to other data on convoy electrons.