Above threshold ionization (ATI) spectra of small metal clusters (e.g., Na 4 and Na 4 + ) are calculated numerically using a spherical jellium model and time-dependent density functional theory for two-color (1064 and 532 nm) ultrashort ͑25 fs͒ laser pulses as a function of phase difference between the two fields. ATI spectra and ionized electron fluxes are obtained in the two opposite directions of the linearly polarized laser fields. The asymmetry, defined as the difference in electron yield, is shown to depend strongly on the carrier-envelope phase of the second-harmonic ͑2͒ field. The ATI spectra allow one to identify the range of kinetic energies of the ionized electrons where the asymmetry mainly occurs. Comparisons are made between calculations with and without self-interaction correction and also with previous exact numerical solutions of the one-electron systems H and H 2 + [A. D. Bandrauk and S. Chelkowski, Phys. Rev. Lett. 84, 3562 (2000)] where such asymmetry effects had first been observed. We find that ATI spectra in the clusters generally have much longer energy plateaus than in previously studied one-electron systems, with cutoffs up to 30-40 times the ponderomotive energy U p . In high-harmonic generation spectra, on the other hand, no extended plateaus are observed.

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Composites of refluxed carbon nanotubes (CNTs) at different contents and orthorhombic tungsten oxide hydrate (WO 3 •H 2 O) were prepared via acid precipitation at room temperature. The CNTs produced a new phase of monoclinic tungsten oxide dihydrate WO 3 •2H 2 O, caused the breakage of WO 3 •H 2 O nanoplates, and affected the microstrain in the nanocomposites. The CNTs also enhanced the absorbance in the visible range and increased the specific surface area and pore volume but abnormally enlarged the optical bandgap, which was assigned to the emerging monoclinic WO 3 •2H 2 O phase. The adsorptivity and photocatalytic activity of the nanocomposites increased remarkably with CNT content. H 2 O 2 strongly enhanced the photocatalytic activity of the pristine and nanocomposite samples, implying the vital role of photogenerated electrons in the photocatalytic process. Among the synthesized samples, the sample with 20 wt.% CNTs showed the highest adsorptivity and photocatalytic efficiency under visible light irradiation. It also exhibited good reusability in methylene blue degradation and applicability in degrading different organic dyes. This study presents a simple method to prepare CNT@WO 3 •H 2 O nanocomposites with a large surface area, a high adsorptivity, and a high photocatalytic activity under visible light irradiation.