Differential cross section ratios for low-energy electron-impact excitation of the 4p(5)5s levels of krypton - sensitive tests of relativistic effects for heavy noble gases

We present new experimental measurements and theoretical calculations of R- matrix and unitarized first-order many-body theory for electron-impact exci tation of krypton. The usefulness of differential cross section ratios in p roviding sensitive tests of electron scattering models for the excitation o f the np(5)(n + 1)s configuration of the heavy rare gases is demonstrated. In addition to differential cross sections alone, these ratios provide inte resting physical insights into the details of the collision process. Compar isons of the measured ratios with predictions from the present and other av ailable calculations show some agreement, but also reveal that significant improvements of these models are required.