Lattice dynamics of ultrathin layers of KBr grown epitaxially on RbCl(001)

Gillman, Edward; Baker, Jenifer M.; Hernández, Jaime J.; Bishop, G. G.; Li, J. A.; Safron, S. A.; Skofronick, J. G.; Bonart, D.; Schröder, U.

doi:10.1103/physrevb.53.13891

Cited by 5 publications

(3 citation statements)

References 35 publications

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“…Further enhancement comes from the so-called penguin diagrams, which induce the O 5 and O 6 operators given below [31]. We employ the values of the coefficients K r evaluated by solving the renormalization-group equations [36,37],…”

Section: Transition Potentialmentioning

confidence: 99%

Nonmesonic weak decay of light hypernuclei with coherent Σ mixing

2002

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Nonmesonic weak decays of the A = 4, and 5 hypernuclei are studied. The short range parts of the hyperon-nucleon weak interactions are described by the direct quark (DQ) weak transition potential, while the longer range interactions are given by the π and K meson exchange processes. Virtual Σ mixings of the coherent type are found to give significant effects on the decay rates of 4 Λ He. A large violation of the ∆I = 1/2 rule is predicted in the J = 0 transition amplitudes. many-body dynamics and nonperturbative QCD effects on hadronic weak interaction are important.Nonmesonic weak decay of hypernucleus is unique as a new type of weak interaction process, which involves only baryons. In weak decays of heavy hypernuclei, pion emissions via Λ → pπ − , nπ 0 are hindered due to the Pauli blocking on the final state nucleon. Instead, the decay is mainly induced by a two-body transition, ΛN → NN, and does not emit pions. This nonmesonic weak baryon-baryon interaction is analogous to the parity violating part of the nuclear force |∆S| = 1 sector.The mechanism of nonmesonic decay of hypernuclei is a long standing problem due to some disagreements between theory and experiment. One of them is the Γ nn /Γ pn ratio, i.e., the ratio of Γ nn = Γ(Λn → nn) and Γ pn = Γ(Λp → pn) transitions. Another, to the validity of ∆I = 1/2 rule. Many studies have been done. The one-pion-exchange (OPE) is the simplest to describe the ΛN → NN transition. It has a similar structure as the OPE in nuclear force and in both of them the tensor transition is strong. As it enhances Γ pn , the Γ nn /Γ pn ratio is suppressed. Typical prediction for OPE is Γ nn /Γ pn ∼ 0.1, while most experimental data indicate Γ nn /Γ pn ∼ 1 or larger [1].In the nonmesonic decay, the Λ-N mass difference is reflected in a high momentum transfer between the baryons, and therefore, short range interaction effects must be important. The lifetime measurements of heavy hypernuclei show saturation at large A and therefore suggest importance of short range interactions [2].An attempt was made in refs. [3,4,5] by considering the effect of the polarization of the pion propagator, which seems to enhance Γ nn /Γ pn slightly. The ρ meson contribution was calculated in refs. [6,7], but it could not reproduce the experimental data. The two-pion exchange and the effective σ meson exchanges [8,9,10] may play an important role because it increases the central attraction which enhances the Γ nn /Γ pn ratio through the enhancement of the J = 0 channels. The pseudoscalar and vector mesons (π, K, η, ρ, ω, and K * ) are considered in [11,12]. The contribution of each meson comes out large, especially for kaon exchange, and significant cancellations between the different contributions are found [13]. The final result is 4-6 times larger than the OPE one [14].Apart from the meson exchange model, several authors pointed out the importance of quark degrees of freedom in baryons [15,16,17,18,19]. Recently we proposed to treat the short range part using the valence quark picture of the baryon and...

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Section: Transition Potentialmentioning

confidence: 99%

Nonmesonic weak decay of light hypernuclei with coherent Σ mixing

2002

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“…Although significant progress has been made in studying RHEED oscillations in epitaxial growth on metals24252627 and semiconductors28293031, there are no reports on halide insulators. Hetero- and homoepitaxial growths of alkali halides using molecular beam epitaxy (MBE) have been studied by both electron and He atom scattering, however with a limited growth parameter range in ultrahigh vacuum32333435363738. In the case of the studies with RHEED in MBE, electron beams had to be removed within seconds to avoid charging, therefore limiting the ability to monitor oscillations and to obtain real time growth mode information.…”

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confidence: 99%

Homoepitaxial Growth of Metal Halide Crystals Investigated by Reflection High-Energy Electron Diffraction

Chen

Kuttipillai

Wang

et al. 2017

Sci Rep

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We report the homoepitaxial growth of a metal halide on single crystals investigated with in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). Epitaxial growth of NaCl on NaCl (001) is explored as a function of temperature and growth rate which provides the first detailed report of RHEED oscillations for metal halide growth. Layer-by-layer growth is observed at room temperature accompanied by clear RHEED oscillations while the growth mode transitions to an island (3D) mode at low temperature. At higher temperatures (>100 °C), RHEED oscillations and AFM data indicate a transition to a step-flow growth mode. To show the importance of such metal halide growth, green organic light-emitting diodes (OLEDs) are demonstrated using a doped NaCl film with a phosphorescent emitter as the emissive layer. This study demonstrates the ability to perform in situ and non-destructive RHEED monitoring even on insulating substrates and could enable doped single crystals and crystalline substrates for a range of optoelectronic applications.

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“…The model parameters are obtained from a least-squares fit of the experimental data for the bulk crystals. Good agreement of calculated surface phonons with helium scattering data is achieved when using the following bulk properties as input data for the fit [9]. 1.…”

Section: Formalismmentioning

confidence: 89%