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Observations on the strong photochromic effect of crystalline TiO 2 quantum dots (mean size ≈ 4 nm) are presented. The synthesized quantum dots consist of irregularly shaped anatase TiO 2 nanoparticles (NPs) and are dispersed in butanol (8% by mass). Obtained NPs exhibit a dramatic photoresponse to UV light, enabling effective transmittance modulation in a broad wavelength range extending from the visible to near-infrared region, and even the thermal black body radiation regime beyond 10 μm. The exceptional photoresponse is attributed to hole-scavenging by butanol, TiO 2 self-reduction, injection of electrons to the conduction band, and consequent localized surface plasmon resonances in NPs. The observed optical effect is reversible, and the initial high transmittance state can be restored simply by exposing the NPs to air. The applied NP synthesis route is economic and can be easily scaled for applications such as smart window technologies.

The total ion and/or electron yield spectra of rare gases Xe, Kr, and Ar have been recorded around the 4d Ϫ1 , 3d Ϫ1 , and 2 p Ϫ1 ionization thresholds, respectively, with very high photon energy resolution at the Finnish beam line at the MAX I storage ring. Linewidths of the excited states are determined for higher excitations than earlier. The widths are observed to differ slightly for each core-excited state.

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