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Difference of the wave-packet dynamics in the ground state and the excited.
| Content Provider | CiteSeerX |
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| Abstract | We investigated temporal evolutions of luminescence spectra in KBr F centers at 5 K using up-conversion spectroscopy technique and observed wave-packet oscillations on the adiabatic potential energy surface in the excited state. The time dependence of the luminescence intensity at 1.05 eV is shown in Fig. 1(b), together with the temporal evolution of the transmission gain in the pump-probe optical-absorption measurements previously reported by Nisoli et al. [1] for comparison (Fig. 1(a)). The oscillatory pattern in Fig. 1(b) is completely different from that in Fig. 1(a). This can be found clearly in the Fourier transformed spectra of each signal. Figure 2(a) and 2(b) show the Fourier power spectra of the oscillatory components in Fig. 1(a) and 1(b), respectively. The highest peak at 3.2 THz in Fig. 2(a) corresponds to the A1g breathing mode of the lattice around the negative vacancy, which is characteristic mode of the F center. In contrary, the predominant peaks are located at 2.6 and 4.8 THz rather than at 3.3 THz in Fig. 2(b). These modes are attributed to the LA phonons near the singularities in (100) and/or (110) crystal directions, and the LO phonons near the Γ point, respectively. The results indicate that in the excited state the local vibration around the center is described as the interaction mode consisting of a linear combination mainly of the bulk phonon modes. Our results undoubtedly reflect the wave-packet dynamics in the excited state, because the detected luminescence energy is far from the energy of the absorption band and close to the peak of the emission band, which corresponds to the potential minimum of the excited state. On the other hand, it is highly possible that the wave-packet dynamics in the ground state was mainly observed in the previously reported absorption measurements, as they were performed under so-called degenerate pump-probe conditions. |
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| Subject Keyword | Wave-packet Dynamic Excited State Ground State Temporal Evolution Up-conversion Spectroscopy Technique Predominant Peak Luminescence Spectrum Bulk Phonon Mode Interaction Mode Luminescence Intensity Wave-packet Oscillation Detected Luminescence Energy La Phonons Time Dependence Pump-probe Optical-absorption Measurement Crystal Direction Negative Vacancy Absorption Band Absorption Measurement Kbr Center Transmission Gain Oscillatory Pattern Potential Minimum Linear Combination Oscillatory Component Emission Band Local Vibration Adiabatic Potential Energy Surface So-called Degenerate Pump-probe Condition Lo Phonons Characteristic Mode Fourier Power Spectrum |
| Content Type | Text |
