Measurement of absolute differential cross sections for the excitation of atomic hydrogen to itsn=2 level by electron impact

Using a crossed-beam method, we have measured absolute differential cross sections for the excitation of atomic hydrogen to its n=2(2²S+2²P) level by electron impact. The angular range covered was from 12^∘{} to 156^∘{} in 12^∘{} increments, while the impact energies treated were 15, 20, 30, and 40 eV. Absolute integrated excitation cross sections were calculated from the differential ones. Agreement of our data with other recent data and calculations is quite good, but there are still some discrepancies among our results and the older data.