EPR of the self-trapped exciton in AgCl

Hayes, W.; Owen, I B

doi:10.1088/0022-3719/9/3/004

Cited by 18 publications

(4 citation statements)

References 11 publications

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“…The same applies for the triplet state of the STE, but here a high-field ͑HF͒ and low-field ͑LF͒ resonance is observed per site, due to the zero-field splitting. 4,5 The isotropic signal at Bϭ3.6130 T ͑gϭ1.878͒ on the right in Fig. 1 is typical for shallow electron centers ͑SEC's͒ which can be of intrinsic or extrinsic nature.…”

Section: Methodsmentioning

confidence: 97%

Spatial distribution of the wave function of the self-trapped exciton in AgCl

et al. 1996

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The results are presented of a high-frequency electron nuclear double resonance ͑ENDOR͒ study of the lowest triplet state of the self-trapped exciton in AgCl. Direct information about the spatial distribution of the wave function is obtained, which confirms that the exciton in its triplet state is built up from a strongly localized self-trapped hole and a very diffuse electron. The electron is mainly contained in a hydrogenlike 1s orbital with a Bohr radius of 15.1Ϯ0.6 Å, but near its center the electron density deviates from spherical symmetry and reflects the D 4h charge distribution of the hole. From a comparison with the results of an ENDOR study of the self-trapped hole, it is concluded that the microscopic and electronic structure of a self-trapped hole is not significantly altered by the attraction of a shallow electron. No evidence is obtained for the formation of Frenkel pairs in AgCl upon ultraviolet irradiation at low temperatures.

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Section: Methodsmentioning

confidence: 97%

Spatial distribution of the wave function of the self-trapped exciton in AgCl

et al. 1996

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“…Recombination of the STE contributes to the broad luminescence band of AgCl crystals at low temperatures, which peaks at about 500 nm, as demonstrated by studies using the method of optically detected magnetic resonance (ODMR). The properties of the excited states of this STE have been the subject of many ODMR investigations [ 11 – 19 ]. However, a number of important questions remained unclear: (1) the structure of the energy levels for STE; (2) the exchange interaction between an electron and a hole in the STE, the ordering of the singlet and triplet sublevels; (3) the dynamical properties of the excited singlet and triplet states; (4) the hyperfine (HF) interaction with the Ag and Cl nuclei; (5) the space distribution of the unpaired electron wave function; (6) the proofs of intrinsic nature of STH and STE; (7) the structure of STE as an STH coupled with an SEC.…”

Section: Introductionmentioning

confidence: 99%

Self-Trapped Excitons in Ionic-Covalent Silver Halide Crystals and Nanostructures: High-Frequency EPR, ESE, ENDOR and ODMR Studies

et al. 2010

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Silver halides have unique features in solid state physics because their properties are considered to be of borderline nature between ionic and covalent bonding. In AgCl, the self-trapped hole (STH) is centered and partly trapped in the cationic sublattice, forming an Ag2+ ion inside of a (AgCl6)4− complex as a result of the Jahn–Teller distortion. The STH in AgCl can capture an electron from the conduction band forming the self-trapped exciton (STE). Recent results of a study of STE by means of high-frequency electron paramagnetic resonance, electron spin echo, electron–nuclear double resonance (ENDOR) and optically detected magnetic resonance (ODMR) are reviewed. The properties of the STE in AgCl crystals, such as exchange coupling, the ordering of the triplet and singlet sublevels, the dynamical properties of the singlet and triplet states, and the hyperfine interaction with the Ag and Cl (Br) nuclei are discussed. Direct information about the spatial distribution of the wave function of STE unpaired electrons was obtained by ENDOR. From a comparison with the results of an ENDOR study of the shallow electron center and STH, it is concluded that the electron is mainly contained in a hydrogen-like 1s orbital with a Bohr radius of 15.1 ± 0.6 Å, but near its center the electron density reflects the charge distribution of the hole. The hole of the STE is virtually identical to an isolated STH center. For AgCl nanocrystals embedded into the KCl crystalline matrix, the anisotropy of the g-factor of STE and STH was found to be substantially reduced compared with that of bulk AgCl crystals, which can be explained by a considerable suppression of the Jahn–Teller effect in nanoparticles. A study of ODMR in AgBr nanocrystals in KBr revealed spatial confinement effects and allowed estimating the nanocrystal size from the shape of the ODMR spectra.

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“…I n pure AgCl, the ODMR spectral features have been interpreted in terms of resonances due to self-trapped holes [3, 41, trapped and free electrons [3, 41, and a selftrapped exciton [5]. Low levels of bromine give rise to a bromine-bound exciton [4,5]. I n this investigation, we have examined nickel-doped AgCl using the ODMR technique.…”

Section: Introductionmentioning

confidence: 99%

“…Low levels of bromine give rise to a bromine-bound exciton [4,5]. I n this investigation, we have examined nickel-doped AgCl using the ODMR technique.…”

mentioning

confidence: 99%