eq. (\[eq.crystal\]). As shown in the middle panel, the calculated spectra show a single-peak in agreement with the experiment. (Only the $\sigma\to\sigma'$ channel gives finite intensity for $\psi=-45^\circ$.) The photon energy dependence in the $\sigma\to\pi'$ channel is found to be the same as in the $\sigma\to\sigma'$ channel in the calculation. On the other hand, an extra peak has been observed in the $\sigma\to\pi'$ channel at $\hbar\omega=7782$ eV (pre-edge peak) for $\psi=0$.[@Hirota] This peak may come from the electric quadrupole ($E_2$) transition.

![ RXS spectra for ${\textbf G}=(00\frac{5}{2})$ at $\psi=-45^\circ$ in the $\sigma\to\sigma'$ channel, as a function of photon energy. Top: experimental spectra at $T=20$ K (Phase II).$^{17)}$ Middle: Calculated spectra by taking account of the direct influence of lattice distortion with $E_d=-0.1$ eV. Bottom: Calculated spectra by taking account of the influence of quadrupole ordering $4f$ states with $E_f/D_f=-0.2$. \[fig.spec\] ](fig.print.5.eps){width="8.0cm"}

![ (a) Main peak intensity as a function of the crystal field parameter $|E_d|$ on the $5d$ states, which is calculated by taking account of the direct influence of lattice distortion. (b) Main peak intensity as a function of the crystal field parameter $|E_f|/D_f$ on the $4f$ states, which is calculated by taking account of the influence of quadrupole 