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Photoelectron spectroscopy data from Bi 2 Sr 2 Ca 12x Y x Cu 2 O 81d single crystals, for x 0, 0.16, and 0.55, are presented. It is shown that there are core level shifts related to the opening of a pseudogap and that similar shifts are observed at the opening of the superconducting gap in optimally doped samples. This result is in agreement with pair formation above T C as suggested by V. J. Emery and S. A. Kivelson [Nature (London) 374, 434 (1995)]. [S0031-9007(97)03557-6]

Polarized far-infrared transmittance spectra of CuGeO3 single crystals were measured at different temperatures (6 K< T < 300 K). Two spectral lines, at 284.2 cm −1 in E||c polarization and at 311.7 cm −1 in E||b polarization, appear at the temperature of the spin-Peierls transition and grow in intensity with decreasing temperature. We assign these spectral features to the folded modes of the dimerized lattice. We discuss a possible role of the spin-phonon interaction in the formation of the 311.7 cm −1 feature.

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