De-excitation process and hot luminescence in the FA(type I) center in KCl:Na

Akiyama, Norio; Muramatsu, Susumu; Baldacchini, G.

doi:10.1016/j.jlumin.2007.10.002

Cited by 4 publications

(3 citation statements)

References 12 publications

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“…Figure 5(c) shows the thus obtained configuration coordinate diagram. Very recently, it has been demonstrated that the anticrossing process also occurs at analogous vacancy centers, the F A (type II) center in KCl : Li [94] and the F A (type I) center in KCl : Na [95]. A series of these studies have indicated that the anticrossing picture is conceivable for the 2s-2p level crossing.…”

Section: S-2p State Mixingmentioning

confidence: 99%

Dynamics of nuclear wave packets at theFcenter in alkali halides

Koyama

Suemoto

2011

Rep. Prog. Phys.

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The F center in alkali halides is a well-known prototype of a strongly coupled localized electron-phonon system. This colour center is one of the long studied targets in the field of photophysics because it is simple but rich in variety. Steady-state spectroscopy, such as modulation spectroscopy and Raman scattering spectroscopy, has elucidated the strength of the electron-phonon coupling in the (meta-)stable state, i.e. the ground state and the relaxed excited state. Picosecond spectroscopy has improved understanding of the state mixing in the transient state. Owing to recent developments of ultrafast lasers with pulse widths shorter than oscillation periods of phonons, it has been possible to perform real-time observation of lattice vibration, and the understanding of the transient state has been remarkably expanded. In this paper, we review early and present studies on dynamics of electron-phonon coupling at the F center, especially recent real-time observations on the dynamics of nuclear wave packets in the excited state of the F center in KI, KBr, KCl and RbCl. These real-time observations reveal (i) spatial extension of the electronic wave function of a trapped electron, (ii) the difference between the coupled phonons in the ground state and the excited state, (iii) diabatic transition between the adiabatic potential energy surfaces and (iv) anharmonicity of the potential energy surface.

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Section: S-2p State Mixingmentioning

confidence: 99%

Dynamics of nuclear wave packets at theFcenter in alkali halides

Koyama

Suemoto

2011

Rep. Prog. Phys.

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“…14 This is a return to GS before reaching C because of the existence of metastable states, such as F A centers. [32][33][34] In this paper, we focus on isolated F centers. Therefore, we pay attention to radiationless processes ͑1͒ and ͑2͒.…”

Section: Introductionmentioning

confidence: 99%

Luminescence efficiency ofFcenters in KI studied by lifetime measurements

2009

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The luminescence efficiency of isolated F centers in KI was studied as a function of the excitation energy by measuring the lifetime for ordinary luminescence. The emission intensity measured under a pulse excitation was found to obey nonexponential decay. The luminescence efficiency decreases to below unity when the excitation energy exceeds 1.96 eV, which corresponds to the slope position at the higher energy side of an F absorption band. The threshold value for the luminescence efficiency is lower than that previously obtained from cw measurements but close to that predicted theoretically by Leung and Song. We have traced the origin of this difference by performing experiments based on the cw method and found out the reason. It is shown that there is a relationship between quantities obtained by the cw method and those obtained by our lifetime measurement. Our experimental data are thoroughly analyzed using a model for the radiationless process of Leung and Song, which is based on a 1s-2p model. A 1s-2p-2s model is also discussed.We have obtained excitation spectra for fast and slow components from the results of A f and A s shown in Fig. 7͑b͒ by using Eqs. ͑A4͒ and ͑A5͒ in Appendix, in which the number of irradiation times n is 87 and the duration time t p is 4.6 s. They are denoted by I cw,f cal and I cw,s cal respectively, and presented in Fig. 8 as a function of the excitation energy, together with the absorption curve of the F band. We see that I cw,s cal well coincides with the F absorption band except for the high-energy side near the K band. This fact means that I cw,s cal is just the excitation spectrum of slow component and the emission of slow component occurs under thermal equilibrium. The other important fact is that I cw,f cal spectrum with the peak of 2.06 eV is not related to the F absorption band. This result suggests that fast and slow components arise from different sources. The deviation of I cw,s cal from the F band in the high-energy side reflects the decrease in s due to radiationless processes.In Sec. IV E, we will show that I cw,s cal agrees with the excitation spectrum obtained by the cw method. C. Dependence of the fast component's lifetime on F center concentrations and temperatures

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“…39͒ and the F A ͑type I͒ center in KCl:Na. 40 A series of these works indicates that the anticrossing picture is conceivable for the first LC. Besides the first LC, the second crossing point has been suggested to exist on the other side of the excited-state APESs ͑Ref.…”

Section: Introductionmentioning

confidence: 99%

Second2s−2plevel crossing at theFcenter in KCl evidenced by frequency upconversion spectroscopy

2009

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Subpicosecond dynamics of resonant secondary emission from the F center in KCl at 5 K is investigated by frequency upconversion method. Detected photon energy range is from 0.65 to 1.55 eV and covers almost all the stationary emission band. The decay time of the luminescence intensity is longer in the low-energy side of emission band than in the high-energy side. A series of transient luminescence spectra shows relatively high intensities in the low-energy side. These two features indicate the existence of the second 2s-2p level crossing near the relaxed excited state.

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De-excitation process and hot luminescence in the FA(type I) center in KCl:Na

Cited by 4 publications

References 12 publications

Dynamics of nuclear wave packets at theFcenter in alkali halides

Dynamics of nuclear wave packets at theFcenter in alkali halides

Luminescence efficiency ofFcenters in KI studied by lifetime measurements

Second2s−2plevel crossing at theFcenter in KCl evidenced by frequency upconversion spectroscopy

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