Glasner-Tompkins relation and reorientation of<i>U</i>centers in LiF crystals

Shalabi, A.S.; Mahdy, A.M. El; Eid, Kh.M.; Kamel, M.A.; El-Barbary, A. A.

doi:10.1103/physrevb.60.9377

Cited by 29 publications

(11 citation statements)

References 22 publications

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“…In other words, the Glasner-Tompkins empirical rule suggests that the energy difference between the fundamental absorption of an alkali halide and the F band is very nearly a function of only the halide species. Exciton band E X , F band E F , E X − E F and E X − E Y for twelve alkali halides have been reported by Malghani and Smith [39] and for LiH and LiF by Shalabi et al [40]. The dependence of the Glasner-Tompkins relation on the dopant cation and surface coordination number (flat, edge and corner) of MgO, KCl and AgBr has also been reported by Shalabi et al [41].…”

Section: Glasner-tompkins Relationmentioning

confidence: 65%

The role of F A1:Ag+ defects in laser light generation and coadsorption of CO and halogen atoms at the KCl and KBr surface sites. First principles calculations

Abdelrazik¹,

Shalabi²

2007

Open Physics

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F A1 :Ag+ color center at the low coordination (100) and (110) surface sites of KCl and KBr thin films play an important role in providing tunable laser oscillation and adsorbatesubstrate interactions. Double-well potentials at this site are investigated using ab initio molecular electronic structure calculations. The calculated Stokes shifted (optical transition bands), opticaloptical conversion efficiencies, the probability of orientational destruction, exciton (energy) transfer and Glasner-Tompkins empirical rule suggest that laser light generation is sensitive to (i) the lattice anion, (ii) the coordination number of surface ions, and (iii) the choice of the basis set centered on the anion vacancy. The adsorbate-substrate interactions were found to be dependent on the electronegativity of the adatom and on the lattice anion. Optimised geometries and the coadsorption of CO and (F, Cl, Br, I) on KCl and KBr (100) crystals are presented. Calculated chemisorption energies for CO on the (halogen atom/defect free sites of KCl and KBr (100) crystals) showed that the coadsorption of halogen atom tends to block other adsorbate-substrate interactions at the nearest neighbour sites. Thus if halogen atom coverage increases, the CO prefers to be adsorbed on the K + site of the KCl and KBr (100) surfaces and on KBr relative to KCl.

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Section: Glasner-tompkins Relationmentioning

confidence: 65%

The role of F A1:Ag+ defects in laser light generation and coadsorption of CO and halogen atoms at the KCl and KBr surface sites. First principles calculations

Abdelrazik¹,

Shalabi²

2007

Open Physics

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“…In other words, the Glasner-Tompkins empirical rule suggests that the energy difference between the fundamental absorption of an alkali halide and the F band is very nearly a function of only the halide species. Exciton band E X , F band E F , E X À E F and hE X À E F i for twelve alkali halides have been reported by Malghani and Smith [32], and for LiH and LiF by Shalabi et al [33]. The dependence of Glasner-Tompkins relation on the dopant cation and surface coordination number of MgO, KCl and AgBr has been reported by Shalabi et al [17][18][19][20].…”

Section: The Glasner-tompkins Relationmentioning

confidence: 76%

The role of type II FB (I):Tl+ defect in laser light generation and color image formation at the low coordination surface sites of AgBr: ab initio calculations

Shalabi

Algaber

Madi

et al. 2006

Current Applied Physics

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“…of the halide species alone. E X , E F , E X -E F , and ͗E X -E F ͘ for twelve alkali halides have been reported by Malghani and Smith,39 and for LiH and LiF by Shalabi et al 40 However, no attempts have been made to clarify the dependence of the Glasner-Tompkins relation on FA centers at the low coordinated surfaces of AgBr.…”

Section: Glasner-tompkins Relationmentioning

confidence: 77%

F_A(I):Au⁺andF_A(II):Cu⁺laser activity and photographic sensitization at the low coordinated surfaces of AgBrab initiocalculations

Shalabi

2002

J Comput Chem

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The twofold potentials of F(A)(I):Au(+) and F(A)(II)Cu(+) color centers at the low coordinated surfaces of AgBr thin films in providing tunable laser activity and photographic sensitization were investigated using ab initio methods of molecular electronic structure calculations. Clusters of variable size were embedded in simulated Coulomb fields that closely approximated the Madelung fields of the host surfaces, and the nearest neighbor ions to the F(A) defect site were allowed to relax to equilibrium in each case. Based on the calculated Stokes shifted optical transition bands and horizontal shifts along the configuration coordinate diagrams, both F(A)(I):Au(+) and F(A)(II):Cu(+) color centers were found to be laser active. The laser activity faded quickly as the bromide ion coordination decreased from 5 (flat) to 4 (edge) to 3 (corner) and as the size of the impurity cation increased from Cu(+) to Au(+). The latter relation was explainable in terms of the axial perturbation of the impurity cation. The smallest calculated Stokes-shift at the corner surface suggested that emission had the same oscillator strength as absorption. All relaxed excited states RESs of the defect containing surfaces were deep below the lower edges of the conduction bands of the defect free ground state surfaces, indicating that F(A)(I):Au(+) and F(A)(II):Cu(+) are suitable laser defects. The probability of orientational destruction of the two centers attributed to the assumed RES saddle point ion configurations along the <110> axis was found to be directly proportional to the size of the impurity cation, with activation energy barriers of about 0.655-3.294 eV for Cu(+), and about 1.887-3.404 eV for Au(+). The possibility of exciton (energy) transfer from the sites of higher coordination to those of lower coordination is demonstrated. The more laser active F(A)(II):Cu(+) center was more easily formed than the less laser active F(A)(I):Au(+) center. The Glasner-Tompkins empirical relation was generalized to include F(A) centers at the low coordinated surfaces of silver bromide thin film. As far as color photographic sensitization is concerned, the lowest unoccupied molecular orbitals of the selected dye molecules in the excited states were high enough for electron injection. F(A) defect formation and rotational diffusion of silver clusters reduced the energy gaps between the excited dye molecules and the lower edges of the conduction bands and allowed for hole injection. About 54-60% of the reduction of silver ions at the flat surface of AgBr was attributed to the host anions and F(A) defect formation, leaving about 40-46% for the reduction of photoelectrons as well as the electrons of the developer or dye molecules. The unrelaxed rotational diffusions of the central Ag(4) by 90 degrees decreased the latter percentage, but were severely hindered by activation energy barriers.

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Glasner-Tompkins relation and reorientation ofUcenters in LiF crystals

Cited by 29 publications

References 22 publications

The role of F A1:Ag+ defects in laser light generation and coadsorption of CO and halogen atoms at the KCl and KBr surface sites. First principles calculations

The role of F A1:Ag+ defects in laser light generation and coadsorption of CO and halogen atoms at the KCl and KBr surface sites. First principles calculations

The role of type II FB (I):Tl+ defect in laser light generation and color image formation at the low coordination surface sites of AgBr: ab initio calculations

F_A(I):Au⁺andF_A(II):Cu⁺laser activity and photographic sensitization at the low coordinated surfaces of AgBrab initiocalculations

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Glasner-Tompkins relation and reorientation ofUcenters in LiF crystals

Cited by 29 publications

References 22 publications

The role of F A1:Ag+ defects in laser light generation and coadsorption of CO and halogen atoms at the KCl and KBr surface sites. First principles calculations

The role of F A1:Ag+ defects in laser light generation and coadsorption of CO and halogen atoms at the KCl and KBr surface sites. First principles calculations

The role of type II FB (I):Tl+ defect in laser light generation and color image formation at the low coordination surface sites of AgBr: ab initio calculations

FA(I):Au+andFA(II):Cu+laser activity and photographic sensitization at the low coordinated surfaces of AgBrab initiocalculations

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F_A(I):Au⁺andF_A(II):Cu⁺laser activity and photographic sensitization at the low coordinated surfaces of AgBrab initiocalculations