Systematic trends in the electronic structure parameters of 4d   transition metal oxides SrMO_{3} (M = Zr, Mo, Ru, and Rh)
  We investigated the electronic structures of the perovskite-type 4$d$ transition metal oxides Sr$M$O$_3$ ($M$ = Zr, Mo, Ru, and Rh) using their optical conductivity spectra $\sigma (\omega)$. The interband transitions in $\sigma (\omega)$ are assigned, and some important physical parameters, such as on-site Coulomb repulsion energy $U$, charge transfer energy $\Delta_{pd}$, and crystal field splitting $10Dq$, are estimated. It is observed that $\Delta _{pd}$ and 10$Dq$ decrease systematically with the increase in the atomic number of the 4$d$ transition metal. Compared to the case of 3$d$ transition metal oxides, the magnitudes of $\Delta_{pd}$ and 10$Dq$ are larger, but those of $U$ are smaller. These behaviors can be explained by the more extended nature of the orbitals in the 4$d$ transition metal oxides. 
Y. S. Lee, J. S. Lee, T. W. Noh, Douck-Young Byun, Kwang Soo Yoo, K.   Yamaura, and E. Takayama-Muromachi