Number of Single, Double, and Triple Clusters in a System Containing Two Types of Atoms

Behringer, R. E.

doi:10.1063/1.1744537

Cited by 224 publications

(57 citation statements)

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“…The populations of the various cluster types are then well known. 9,11 As discussed later, deviations from a random distribution can be detected by analyzing the measured magnetization curve at low temperatures. The ability to detect such deviations is a major advantage.…”

Section: Theorymentioning

confidence: 99%

Eu-Eu exchange interaction and Eu distribution inPb1−xEuxTefrom magnetizatio

et al. 1997

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The magnetization of Pb1−xEuxTe samples with x = 1.9, 2.6 and 6.0% was measured at 20 mK in fields up to 50 kOe, and at 0.6 K in fields up to 180 kOe. The 20 mK data show the magnetization steps (MSTs) arising from pairs and from triplets. The pair MSTs are used to obtain the dominant Eu-Eu antiferromagnetic exchange constant, J/kB = −0.264 ± 0.018 K. The exchange constant for triplets is the same. Comparison of the magnetization curves with theoretical simulations indicates that the Eu ions are not randomly distributed over all the cation sites. The deviation from a random distribution is much smaller if J is assumed to be the nearest-neighbor exchange constant J1 rather than the next-nearest-neighbor exchange constant J2. On this basis, J is tentatively identified as J1. However, the possibility that J = J2 cannot be excluded completely. To obtain agreement with the data, it must be assumed that the Eu ions tend to bunch together. Comparision with microprobe data indicates that the length scale for these concentration variations is smaller than a few µm. The theoretical simulations in the present work improve on those performed earlier by including clusters larger than three spins.75.50. Pp, 75.30.Et, 75.60.Ej

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Section: Theorymentioning

confidence: 99%

Eu-Eu exchange interaction and Eu distribution inPb1−xEuxTefrom magnetizatio

et al. 1997

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“…Already in 1958 Behringer was able to calculate the number of single-ions and pair-ions that one expects for a certain percentage of dopants introduced in the lattice [22]. These numbers have been compared with experimental results obtained from luminescence measurements (on Gd 3+ doped Lu 2 O 3 and other rare-earth compounds [23]) and good agreement has been found.…”

Section: Pair-states In a Bulk Crystalmentioning

confidence: 73%

Synthesis, simulation & spectroscopy: physical chemistry of nanocrystals

Suyver

2003

Spectroscopy of Systems With Spatially Confined Structures

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Experiments on nanocrystalline semiconductors form a wide and rapidly expanding field of research. This chapter concentrates on two very different topics within this field. In the first part, pair formation of dopant ions in nanocrystals is discussed. After a general introduction on the influence of pair formation on the luminescence properties, pair formation in nanocrystals is discussed. Due to a difference between the connectivity for sites in the bulk and at the surface, the fraction of dopant pairs depends on the crystallite size. Simulations of the statistical distribution of dopant pair states in a nanocrystal as a function of crystal structure, size and dopant concentration are presented. A closed form approximation for the results of the simulations is derived and the validity is tested. The work presented can be used to estimate dopant pair concentrations in the case of random substitution or a lower limit for the pair concentration if preferential pair formation occurs.The second part of the chapter discusses the luminescence of a single nanocrystalline semiconductor particle. The absence of inhomogeneous broadening and other ensemble averaging effects has provided exciting new insight into the luminescence and quenching mechanisms. The linewidth, blue shift and bleaching of the luminescence of single CdSe/ZnS core/shell nanocrystals are shown and discussed. Finally, potential applications of nanocrystals as luminescent labels in biological systems are presented and a few challenges for future research are discussed.

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“…It restricts chemical interactions to the primary interactions only, because in most cases, there is no other molecule or radical in range that effectively results in the stabilization of the radicals formed inside the matrix. In our case, ∼90% of the C 2 H 2 molecules are isolated in the matrix, while the rest exist as small clusters (Behringer 1958).…”

Section: Ar:c 2 H 2 Resultsmentioning

confidence: 99%

Vacuum ultraviolet photochemistry of solid acetylene: a multispectral approach

Cuylle

Zhao

Strazzulla

et al. 2014

A&A

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Aims. Gas phase acetylene (C 2 H 2 ) and polyynes (H(-C≡C-) m H) are ubiquitous in the interstellar medium. However, astrochemical models systematically underestimate the observed abundances, supporting the idea that enrichment from the solid state takes place. In this laboratory-based study, we investigate the role C 2 H 2 plays in interstellar ice chemistry and we discuss the way its photoproducts may affect gas phase compositions. Methods. C 2 H 2 ice is investigated under vacuum ultraviolet (VUV) irradiation in its pure form as present in the atmosphere of Titan and in a water-dominated ice as present on grain mantles in molecular clouds and on comets. To disentangle the photochemical network, a unique, complementary combination of infrared and ultraviolet-visible (UV-VIS) spectroscopy is used. Results. From the experimental results, it can be concluded that the VUV-induced solid state C 2 H 2 reaction network is dominated by polymerization resulting in the formation of polyynes at least up to C 20 H 2 and larger polyyne-like molecules. At low temperatures, this process takes place very efficiently and suggests low barriers. When extending this reaction scheme to a water-rich environment, the dominant reaction products are CO and CO 2 but the simultaneous detection of polyyne like molecules is evidence that the reactions as observed in pure C 2 H 2 ice persist. Conclusions. From the spectroscopic evidence as presented in this laboratory study, it is concluded that the formation of polyynes upon VUV irradiation of interstellar ices is a process that may contribute to at least part of the observed gas phase enrichment in space.

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Number of Single, Double, and Triple Clusters in a System Containing Two Types of Atoms

Cited by 224 publications

References 1 publication

Eu-Eu exchange interaction and Eu distribution inPb1−xEuxTefrom magnetizatio

Eu-Eu exchange interaction and Eu distribution inPb1−xEuxTefrom magnetizatio

Synthesis, simulation & spectroscopy: physical chemistry of nanocrystals

Vacuum ultraviolet photochemistry of solid acetylene: a multispectral approach

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