6pphotoionization in high-Zelements and the influences of relativistic Cooper minima

Relativistic Dirac-Slater calculations of the photoionization of the $6p$ subshell in elements in the range $82\le Z\le 100$ have been performed, examining cross sections, branching ratios, and angular distributions. The zero (Cooper minimum) which appears in the $6p\to \epsilon d$ nonrelativistic matrix element is split into three relativistically, for the matrix elements $6p_{\frac{3}{2}}\to \epsilon d_{\frac{3}{2}}$, $6p_{\frac{3}{2}}\to \epsilon d_{\frac{5}{2}}$, and $6p_{\frac{1}{2}}\to \epsilon d_{\frac{3}{2}}$. The outstanding feature of our results is the huge energy splitting between these minima, more than an order of magnitude larger than the discrete $6p_{\frac{3}{2}}-6p_{\frac{1}{2}}$ splitting. The origin of this phenomenon is discussed along with its consequences for angular distributions and branching ratios.