Angular distributions of Xe $5s\to \epsilon p$ photoelectrons were measured with use of pulsed synchrotron radiation and a time-of-flight photoelectron spectrometer. The asymmetry parameters ${\beta }_{5s}$ differ markedly from the nonrelativistic value of 2, particularly near the Cooper minimum, in agreement with $\mathrm{jj}$-coupling models. This confirms calculations based on the relativistic random-phase-approximation model of Johnson and Cheng, establishing the importance of the interchannel coupling in $5s\to \epsilon p$ photoionization.

• Received 9 October 1979

DOI:https://doi.org/10.1103/PhysRevLett.43.1661