Lifetime Studies on the Relaxed Excited State of Color Centers

Self Cite

New results on the temperature-dependence of the lifetime of the F-center in NaBr are obtained by luminescence measurements. The disexcitation energy is evaluated to (0.078 & 0.006) eV. A fast component ((22.951) ns) of the decay spectra is attributed to the M-center. The data are discussed in respect of previous photoconductivity measurements and of the criterion of occurrence of F-center luminescence in ionic crystals.Au moyen de mesures de luminescence on a obtenu des rCsultats experimentaux noiiveaiix siir la durBe de vie du centre F excitB dans le NaBr en fonction de la temperature. On a evalub une Bnergie de dhsactivation de (0,078 f 0,006) eV. Une composante rapide ((22.9 & 1) ns) de la distribution de l'emission dans le temps a Btk attribuB au centre M. La, discussion des donnbes experimentales est faite en tenant compte de mesures de photoconductivitb effectubes en precedance e t du critere pour l'existence de luminescence de centres F dans les cristaux ioniques.

Section: Experimental Data and Discussionmentioning

confidence: 99%

Section: A Refined Version Of the Dexter Et Al [L] Model Was Introdumentioning

confidence: 98%

Lifetime of Color Centers in NaBr

Bosi

Longoni

Nimis

1978

Self Cite

“…They suggested this could be explained by a fast radiationless transition from the second to the first excited state. The temperature dependence of the emission lifetime was also investigated by Bosi et al [4]. They found the lifetime was independent of temperature up to about room temperature, which is consistent with the photolytic stability of the F, centre.…”

Section: Introductionmentioning

confidence: 72%

Radiation‐Induced Emission of F₂ Centres in KCl

Chandratillake

Newton

Robinson

et al. 1980

An emission has been observed in KCl single crystals subjected to 12 MeV electron pulses. The emission spectrum peaks at 1200 nm (1.03 eV) and has a temperature-independent lifetime of 29.7 ns up to room temperature. Experiments with crystals previously irradiated to produce F and F2 centres showed that the emission mainly arose from direct excitation by the electron pulse of previously existing F2 centres. The lifetime data, but not the spectrum, are in good agreement with published data.Es wird eine Emission in KC1-Einkristallen, die 12 MeV-Elektronenimpulsen ausgesetzt sind, beobachtet. Das Emissionsspektrum hat ein Maximum bei 1200 nm (1,03 eV) und eine temperaturunabhangige Lebensdauer von 29,7 ns bis Zimmertemperatur. Versuche mit vorbestrahlten Kristallen, um F-und F,-Zentren zu erzeugen, zeigen, daB die Emission hauptskichlich aus der direkten Anregung durch den Elektronenimpuls aus schon existierenden F,-Zentren herriihrt. Die Lebensdauerwerte, jedoch nicht das Spektrum, befinden sich in guter Ubereinstimmung mit publizierten Werten.

“…The experiniental technique was essentiallv the same as that deiwribed in [8]: that is, the measurement of the single-photon delay distribution (SPDD) in respect of pulsed excitation. I n the excitation channel we used a 340 nm interferential filter, whereas in the detection channel we used a 24 Wratten-Kodak optical filter, which gives constant transmission over the whole wavelength region where the F-center emission band is placed.…”

Section: Experimental Results and Discussioilmentioning

confidence: 99%

More on the F‐Center Decay in Additively Colored NaF:LiF

Bosi

Gagliardelli

Nimis

1983

Self Cite

Accurate measurements of the F-center lifetime, z ( T ) , in additively colored NaF: LiF samples are presented as a function of the temperature, starting from 7.6 K. The anomalous behavior of the F-center decay in NaF is confirmed only as regards the behavior of the relative quantum yield ~~( 2 " ): the presence of another decay channel for the F-center electron, besides the jumping into the conduction band, is evidenced. The disagreement with data obtained by other authors is explained by the presence of aggregate centers in their samples. A z(!P)/r],(T) behavior contrary t o that presented by Stiles, Fontana, and Fitchen is observed. A critical review of models and guesses proposed in the literature is also presented in order to obtain a correct understanding of the nature of the relaxed excited state of the F-center.Dans ce travail on pr6sente des mesures accurBes, en fonction de la temperature, de vie moyenne du centre F, pour des Bchantillons de NaF:LiF additivement colorbs, & partir de 7,G K. Le eomportement irrBgulier du centre F in NaF est confirm6 seulement si on considhe le rendement quantique 7lr(T) : d'autre partie on a mis en evidence la pr6sence d u n autre canal de dBsexcitation pour 1'Bleetron du centre F, au deli du ,,jump" dans la bande de conduction. Le dbsaccord trouvB avee les donnBes obtenues par d'autres auteurs est expliqu6 par la presence de centres complexes dans leur Bchantillons. On a observB, egalement, un comportement t( T)/q,(T) contraire B celui present6 par Stiles, Fontnna et Fitchen. On presente, finalement, ime revision critique des modhles et des tentative8 d'interprbtation proposBs dans la litterature dam le but dobtenir une comprehension correcte de la nature de 1'Btat excite relax6 du centre F.