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We have studied the optical recombination channels of TbCl3 using x-ray excited optical luminescence at the N4,5 absorption edge of Tb (giant resonance) in both the energy and time domain. The luminescence exhibits a relatively fast 5D3, and a slow 5D4 decay channel in the blue and green, respectively. The rather short lifetime of the 5D3 state indicates that the decay is mainly driven by Tb-Tb ion interaction via non-radiative energy transfer (cross-relaxation). At the giant resonance the X-ray Absorption Near Edge Structure (XANES) recorded using partial photoluminescence yield is inverted. In the pre-edge region the contrast of the spectral feature is significantly better in optical XANES than in total electron yield. Changes in the intensity of 5D3-7F5 (544 nm) and 5D4-7F6 (382 nm) optical transitions as the excitation energy is tuned across the giant resonance are also noted. The results provide detailed insight into the dynamics of the optical recombination channels and an alternative method to obtain high sensitivity, high energy resolution XANES at the giant resonance of light emitting rare-earth materials. [ABSTRACT FROM AUTHOR]

Time-resolved x-ray excited optical luminescence (XEOL) and x-ray absorption near edge structures have been employed to study the origin of the multicolor luminescence from SnO2 nanoribbons. The authors find that the yellow-green luminescence has a long lifetime while the blue luminescence a short one. The luminescence is attributed to the radiative decay of trapped electrons in oxygen vacancies just below the conduction band and electrons in the conduction band to intrinsic surface states in the band gap. [ABSTRACT FROM AUTHOR]

We have monitored the optical luminescence from ZnS nanowires as a function of x-ray energy at the Zn L edge (1022 eV). The x-ray absorption spectrum obtained using the 338 nm, band edge emission as a signal resembles that of the wurtzite form of ZnS, while that obtained using the 430 and 520 nm defect emissions, resembles that of the sphalerite phase. Wurtzite is the dominant phase of the wire, while sphalerite is only found at the end of the wire adjacent to the gold particle used for nucleation and in small, highly localized regions of the wire. Therefore, the present results support the idea that the defect luminescence centers are caused by Au ions (520 nm) and vacancies (430 nm), which are located in regions of sphalerite and show how x-ray excited optical luminescence may be used to probe the local environment of such centers. [ABSTRACT FROM AUTHOR]

We have monitored the changes that occur in the x-ray-excited optical luminescence, absorption, and photoemission spectra as a function of vacuum annealing time and temperature for ZnS nanowires. All measurements were done in situ. Initial heating causes desorption of surface oxides and a concurrent reduction in the intensity of all the luminescence peaks, which we attribute to the creation of surface states that quench the luminescence. Extended annealing causes diffusion of Au from the particle used to nucleate the wire growth, which results in an increase in intensity of its associated luminescent band at 520 nm. Changes were also observed in the Zn L- and S K-edge x-ray absorption spectra, which are consistent with this interpretation. [ABSTRACT FROM AUTHOR]