Photoionization of the Ba 6s6p1P1state

In an effort to explain two disagreeing experimental measurements of photoionization cross sections, we employ an eigenchannel R-matrix approach using a jj-coupling basis set to calculate the photoionization of the excited state 6s6p ${}_{}{}^1{}_{}{}^{}$ ${\mathit{P}}_1$ of barium from threshold to about 3-eV photoelectron energy. The calculated cross section shows rich structure due to the breakdown of the LS coupling and mixing of several Rydberg series. Our results are in approximate agreement with one measurement farther from threshold, but indicate that the absolute normalization of another measurement at and around threshold is in error.