Phonon sideband optical spectroscopy determines the energy of the dark K-momentum exciton for (6,5) carbon nanotubes. One-phonon sidebands appear in absorption and emission, split by two zone-boundary (K-point) phonons. Their average energy locates the E11 K-momentum exciton 36 meV above the E11 bright level, higher than available theoretical estimates. A model for exciton-phonon coupling shows the absorbance sideband depends sensitively on the K-momentum exciton effective mass and has minimal contributions from zone-center phonons, which dominate the Raman spectra of carbon nanotubes.

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We describe a novel purification process for single-wall carbon nanotube (SWNT) materials that removes non-nanotube carbon and reduces ferromagnetic impurities to levels at which native SWNT magnetic properties predominate. Ferromagnetism is reduced from 1.04 to less than 0.013 emu/g by magnetic gradient filtration. This procedure creates samples of sufficient quality for spectroscopies such as nuclear magnetic resonance (NMR). The overall cleanliness and purity of the material is confirmed through NIR absorption spectroscopy, X-ray diffraction, C 60 filling experiments with yields exceeding 90%, and highresolution 13 C NMR.

The magnetic properties of small diameter semiconducting single-walled carbon nanotubes have been recently predicted to depend sensitively on structural details that can be ignored for larger diameters. We confirm this dependence by directly measuring the magnetic alignment of several species of carbon nanotubes in aqueous suspension using polarized resonant photoluminescence. These data show evidence for asymmetry between nanotube chirality subclasses and are used to construct a model predicting nanotube magnetic responses for arbitrary semiconducting chirality.

We perform pump-probe Kerr spectroscopy in the colossally magnetoresistive manganite Pr 0.67 Ca 0.33 MnO 3 . Kerr effects uncover surface magnetic dynamics undetected by established methods based on reflectivity and optical spectral weight transfer. Our findings indicate the connection between spin and charge dynamics in the manganites may be weaker than previously thought. Additionally, important differences between this system and conventional ferromagnetic metals manifest as long-lived, magneto-optical coupling transients, which may be generic to all manganites.

Pump-probe Kerr spectroscopy reveals evidence for transient photoinduced magnetization (PIM) near T c in the colossally magnetoresistive manganite La 0.7 Ca 0.3 MnO 3. For temperatures above T c , the PIM signature reaches full strength at the field-driven magnetic phase transition, while below T c it exhibits a magnetic activation threshold of ~0.5 T. We compare the temperature dependence of the effect with diffuse spin scattering previously measured with neutrons and discuss these findings in the context of phase separation near T c. Comments

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