Charge Transfer into Excited States of Hydrogen by Low Energy Protons Incident on Gases

Cross section measurements performed at East Texas State University are presented for electron capture into 3s and 4s states of hydrogen for 10-150 keV protons incident on noble gases. The measurement technique and some of its limitations are described. The cross section values obtained are compared to existing measurements and examined in light of certain theoretical predictions. At the higher energies of this study we suggest that the 3s and 4s states dominate capture into the n=3, and n = 4 levels. We also find that the n-3 scaling law is compatible with these measurements over a wide range of energies. The absolute values as well as the general shape of these excitation functions indicate that the internal structure of the target atom is an important factor in the charge transfer process.