Calculation of Rydberg energy levels for the francium atom

Based on the weakest bound electron potential model theory, the Rydberg energy levels and quantum defects of the $n$p$^{2}$P$^{\rm \circ}_{1 / 2}$ ($n$=7--50) and $n$p$^{2}$P$^{\rm \circ}_{3 / 2}$ ($n$=7--50) spectrum series for the francium atom are calculated. The calculated results are in excellent agreement with the 48 measured levels, and 40 energy levels for highly excited states are predicted.