The electronic structures of undoped and fluorine-doped LaFeAsO superconductors and fluorine-doped SmFeAsO superconductors are studied using soft x-ray absorption and emission spectroscopy combined with full potential linearized augmented planes waves ͑FP LAPW͒ calculations. The comparison between the numerical simulations and the experimental Fe L-emission spectra shows that the Fe states are concentrated near E F , suggesting that the materials are not highly correlated systems. The comparison of the O K-edge and F K-edge spectra with the calculated density of states shows that the F dopants do not directly participate in the electronic structure near E F , and so they serve the same purpose as an oxygen vacancy leading to an increase in the number of available charge carriers. Increasing the amount of fluorine doped into the structure of SmFeAsO is shown to cause a narrowing of the bandwidth of occupied O valence states.

Raman spectra are reported for Ba-doped fullerides Ba x C 60 (xϭ3, 4, and 6͒. The lowest-frequency H g modes split into five components for Ba 4 C 60 and Ba 6 C 60 even at room temperature, allowing us a quantitative analysis based on the electron-phonon coupling theory. For the superconducting Ba 4 C 60 , the density of states at the Fermi energy was derived as 7 eV Ϫ1 , while the total value of electron-phonon coupling was found to be 1.0, which is comparable to that of K 3 C 60 . The tangential A g (2) mode, which is known as a sensitive probe for the degree of charge transfer on C 60 molecules, shows a remarkable shift depending on the Ba concentration, being roughly consistent with the full charge transfer from Ba to C 60 . An effect of hybridization between Ba and C 60 orbitals is also discussed.

have been characterized by x-ray-diffraction and Ramanscattering measurements. It is found that the c-axis parameter decreases with increasing doping concentration ͑Pr or La͒ or oxygen content. The softening of the O(2) Sr A g mode corresponds to the decrease of the c-axis parameter. The effect of Pr substitution for Ca on this mode is smaller than that of La substitution for Sr. The shift of the O(1) Cu B 1g mode is related to the ionic size of the doping element. The O(3) Bi A g mode does not exhibit remarkable frequency shift since the Bi-O(3)-Bi force constant nearly remains unchanged upon doping. The effect of oxygen content on the O(2) Sr A g mode in the Bi2212 system is in contrast to that on the corresponding O(4) Ba A g mode in the Y123 system. Change in valence is the dominating effect causing the frequency shift of the O(2) Sr A g mode.