Speculations on the absorption and emission properties of the F-centre in alkali halides

Gallo

et al. 2001

phys. stat. sol. (b)

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A review of the relevant data concerning the decay properties of the Cu þ fluorescence in alkali halides is presented. A critical analysis of the experiments reported in literature shows that the problem of the correct and complete interpretation of the Cu þ fluorescence was made complicated in the past essentially because of historical reasons. The validity of the decay models was ascertained by the authors by simultaneously detecting both lifetime and quantum yield during each set of measurements as a function of the temperature.

Section: Introduction: the Historymentioning

confidence: 99%

“…[6]). Sanderson developed a simple empitical formula to quantify the variation of the ionic radius r with the partial charge, r ¼ r c À Bd, where r c is the nonpolar covalent radius, B a constant for a particular atom; r attains the limit (ionic) value r i if AEd is equal to unity.…”

Section: Introduction: the Historymentioning

confidence: 99%

Review of Emission and Lifetime Data Concerning Cu+ Fluorescence in Alkali Halides

Gallo

et al. 2001

phys. stat. sol. (b)

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“…Furthermore, a good fit was found [21], i.e. the experimental H,,(F) values measured at the lowest temperature are simply proportional to the w,,(F) ones by assuming an S value (z 43.13) equal to the mean of the observed S values; we can now write this relationship as follows:…”

Section: Trends Andcorrelations Concerning M-centre Emission Propertimentioning

confidence: 98%

On the M‐Centre Luminescence in Alkali Halides. The Case of NaF and LiF

Physica Status Solidi (b)

Gallo

1994

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“…Recently, in color center as well as in defect physics, we adopted [4] the Sanderson model for nonmolecular structures which utilizes an unequivocal scheme in determining the ionic radii; we obtained predictions for off-center configurations of impurity ions in alkali halides and oxides [4], for FA (II-type) center formation [5] and for F-center luminescence quantum yield [6] in alkali halides (incidentally, it should be remembered that we found [7] also a correlation between the Sanderson partial charge and the Szigeti effective charge).…”

mentioning

confidence: 99%

“…We restricted our attention to NaCl structure crystals since, unfortunately, only few accurate values for ionic radii have been obtained for CsCl structure crystals [4] by using with 1 = 0 for group IV, I) Piazza Leonard0 da Vinci 32, 1-20133 Milano, Italia. ' ) Work jointly supported by the Minister0 della Pubblica Istruzione and by Consiglio Nazionale delle Ricerche, Gruppo Nazionale di Struttura della Materia.…”

mentioning

confidence: 99%

Empirical Calculation of the Bulk Modulus for the Alkali Halide Crystals

Physica Status Solidi (b)

1993

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Cohen [l] predicted that the zero pressure isothermal bulk modulus B, of group IV, III-V, and V-VI semiconductor crystals, near the center of the periodic table, with the diamond and zincblende structures, should scale as B, = where d is the nearest neighbor distance (in A) and a = 1761 GPa w3.'.Subsequently Lam et al. [2] found that the bulk modulus scaled as B , = (1971 -2202) x = 1 for III-V, and 1 = 2 for II-VI semiconductors. The accuracy of the above formula in predicting the bulk modulus is remarkably good with only small percentage error for most of the materials examined.Recently Schlosser [3] found a similar scaling for the NaCl and CsCl structure in alkali halide crystals; the product P = Bod -35 is, to a good approximation, constant within each family with a common cation (Li, Na, K, Rb, Ag, Cs, T1) and a common crystal structure.Nevertheless, Schlosser [3] did not give any physical explanation for this occurrence, in particular for the dependence of P on the kind of cation. Recently, in color center as well as in defect physics, we adopted [4] the Sanderson model for nonmolecular structures which utilizes an unequivocal scheme in determining the ionic radii; we obtained predictions for off-center configurations of impurity ions in alkali halides and oxides [4], for FA (II-type) center formation [5] and for F-center luminescence quantum yield [6] in alkali halides (incidentally, it should be remembered that we found [7] also a correlation between the Sanderson partial charge and the Szigeti effective charge).Thus, we looked for a dependence of B, not only on the lattice parameter d but also on the ionic radius (the latter plays the role of a corrective effect).Indeed, since the applicability of the Cohen relationship is essentially restricted [l, 21 to covalent compounds, we expect a dependence of B, on the ionic bonding, which implies, in the framework of the Sanderson model, the dependence on the partial charge and on the ionic radius.In Table 1 . We restricted our attention to NaCl structure crystals since, unfortunately, only few accurate values for ionic radii have been obtained for CsCl structure crystals [4] by using with 1 = 0 for group IV,