Atomic hydrogen and muonium in alkali halides

Spaeth, J.‐M.

doi:10.1007/bf02394969

Cited by 18 publications

(12 citation statements)

References 36 publications

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“…Atomic hydrogen atoms have been trapped in many matrices at cryogenic temperatures, but only in octasilsesquioxane are they stable for years. In alkali halides they are unstable above 165 K [45], and in quartz they disappear above 100–120 K [46; 47]. In calcium phosphate their half life at room temperature is about 4 days [48].…”

Section: Discussionmentioning

confidence: 99%

Atomic hydrogen as high-precision field standard for high-field EPR

Stoll

Ozarowski

Britt

et al. 2010

Journal of Magnetic Resonance

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We introduce atomic hydrogen trapped in an octaisobutylsilsesquioxane nanocage (H@iBuT 8 ) as a new molecular high-precision magnetic field standard for high-field EPR spectroscopy of organic radicals and other systems with signals around g = 2. Its solid-state EPR spectrum consists of two narrow lines separated by about 51 mT and centered at g ≈ 2. The isotropic g factor is 2.00294(3) and essentially temperature independent. The isotopic 1 H hyperfine coupling constant is 1416.8(2) MHz below 70 K and decreases slightly with increasing temperature to 1413.7(1) MHz at room temperature. The spectrum of the standard does not overlap with those of most organic radicals, and it can be easily prepared and is stable at room temperature.

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Section: Discussionmentioning

confidence: 99%

Atomic hydrogen as high-precision field standard for high-field EPR

Stoll

Ozarowski

Britt

et al. 2010

Journal of Magnetic Resonance

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“…The same is true of alkali halides, where a more extensive comparison is possible. For these materials, H is known to ESR in every member of the family; there is greater deviation of the hyperfine constants from the free-atom value and the variation is exactly mimicked in muonium spectroscopy (Spaeth 1986, Baumeler et al 1986. In semiconductors, notably silicon, where states of greater delocalization are found, the similarity extends from the hyperfine spectroscopy (reflecting details of electronic structure) to the actual positions of deep donor and acceptor levels in the energy gap (Lichti 1995, Bonde Nielson et al 1999.…”

Section: Oxide Muonicsmentioning

confidence: 99%

Oxide muonics: II. Modelling the electrical activity of hydrogen in wide-gap and high-permittivity dielectrics

Cox

Gavartin

Lord

et al. 2006

J. Phys.: Condens. Matter

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Following the prediction and confirmation that interstitial hydrogen forms shallow donors in zinc oxide, inducing electronic conductivity, the question arises as to whether it could do so in other oxides, not least in those under consideration as thin-film insulators or high-permittivity gate dielectrics. We have screened a wide selection of binary oxides for this behaviour, therefore, using muonium as an accessible experimental model for hydrogen. New examples of the shallow-donor states that are required for n-type doping are inferred from hyperfine broadening or splitting of the muon spin rotation spectra. Electron effective masses are estimated (for several materials where they are not previously reported) although polaronic rather than hydrogenic models appear in some cases to be appropriate. Deep states are characterized by hyperfine decoupling methods, with new examples found of the neutral interstitial atom even in materials where hydrogen is predicted to have negative-U character, as well as a highly anisotropic deep-donor state assigned to a muonium-vacancy complex. Comprehensive data on the thermal stability of the various neutral states are given, with effective ionization temperatures ranging from 10 K for the shallow to over 1000 K for the deep states, and corresponding activation energies between tens of meV and several eV. A striking feature of the systematics, rationalized in a new model, is the preponderance of shallow states in materials with band-gaps less below 5 eV, atomic states above 7 eV, and their coexistence in the intervening threshold range, 5-7 eV.

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“…Further reduction of spin density on the proton implies a degree of covalency or bonding between the hydrogen atom and the host atoms. The alkali halides provide a good example, where the variation of hyperfine constants for H is closely mimicked by values for Mu Y albeit with an almost uniform scaling factor of 98% that can be traced to the greater zero point energy of muonium, as can the similar isotope effect between H and Mu in quartz [3,7,8]. The isotope and other dynamical effects are treated in detail by Roduner et al [9].…”

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confidence: 94%

The Systematics of Muonium Hyperfine Constants

Cox

Johnson

2004

Hyperfine Interact

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The hyperfine constants for muonium in elemental and binary inorganic solids suggest formation of three different families of defect centre, with distinct electronic structures. The overall range of values, spanning nearly five orders of magnitude, and their correlation with host properties such as band gap and electron affinity, reveal a deep-to-shallow instability which has profound implications for the electrical properties of hydrogen impurity in electronic materials, both semiconducting and dielectric.Abbreviations: "SR Y muon spin rotation, relaxation and resonance. Nomenclature:Mu Y chemical symbol for muonium, light pseudo-isotope of hydrogen. This paper draws attention to the wealth of hyperfine data which now exists for muonium defect centres in solids, and to the consequent value of muonium as a model for hydrogen in materials where ESR data for hydrogen itself are not available. It highlights important and highly topical new additions to this data base, otherwise accumulated over three decades of "SR spectroscopy, and reYexamines which material parameters control the variation of hyperfine constant. The first point to make is that this variation is huge, spanning almost five powers of ten. Thus muonium in quartz or silica has a hyperfine constant close to the freeYatom value of 4.45 GHz [1] and its spectrum is visible up to at least 1000 K; in striking contrast, muonium in zinc oxide has a contact term of just 0.5 MHz and disappears around 35 K with an ionization energy of a few tens of meV only [2]. Hydrogen counterparts for both states are known to ESR spectroscopy [3,4]. The one extreme corresponds to trapped atoms in which the 1s(Mu) or 1s(H) orbitals are confined to interstitial cages in the host lattice, the other to delocalization of the shallow-donor type, in which the orbital is dilated by the the bulk dielectric constant of the medium and, where appropriate, by a low effective mass of the electron.The question arises whether all intermediate degrees of delocalization of the unpaired electron are permitted, in a continuum between these extremes. It

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Atomic hydrogen and muonium in alkali halides

Cited by 18 publications

References 36 publications

Atomic hydrogen as high-precision field standard for high-field EPR

Atomic hydrogen as high-precision field standard for high-field EPR

Oxide muonics: II. Modelling the electrical activity of hydrogen in wide-gap and high-permittivity dielectrics

The Systematics of Muonium Hyperfine Constants

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