Generalized oscillator strengths in the electron impact spectra of rubidium and caesium

Studies of generalized oscillator strengths as a function of incident electron kinetic energy within the range 33·5-100·5 eV have been made for rubidium and caesium using a crossed-beam high-resolution electron energy-loss spectrometer. Absolute generalized oscillator strengths have been derived by normalizing the resonance transition to the optical oscillator strength. For rubidium the reduced matrix elements (5 2 Sparallel r 2 parallel6 2 S) and (5 2 Sparallel r 2 parallel7 2 S) were found to be 44 A.U. ±25% and 15 A.U. ±40%, respectively, and the transition probabilities A (4 2 D -> 5 2 S) and A (5 2 D -> 5 2 S) found to be 204 s -1 ±10% and less than 24 s -1 , respectively. For caesium the reduced matrix element (6 2 Sparallel r 2 parallel7 2 S) was found to be 57 A.U. ±20%, and the transition probabilities A (5 2 D -> 6 2 S), A (6 2 D -> 6 2 S) and A (7 2 D -> 6 2 S) were found to be 49 s -1 ±10%, 94 s -1 ±20% and 80 s -1 ±40%, respectively.