Grundlagen und Anwendungen der Mössbauerspektroskopie

Barb, D.

doi:10.1515/9783112544167

Cited by 41 publications

(10 citation statements)

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“…Mössbauer spectra were theoretically reproduced using the Pi program package developed by U. von Hörsten (von Hörsten (2019)). All values for the isomer shift δ are given relative to that of α-Fe at room temperature (δ α−Fe = −0.107 mm/s) (Barb (1980)).…”

Section: Mössbauer Spectroscopy Measurementsmentioning

confidence: 99%

Drifting inwards in protoplanetary discs I Sticking of chondritic dust at increasing temperatures

Bogdan

Pillich

Landers

et al. 2020

A&A

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Sticking properties rule the early phases of pebble growth in protoplanetary discs in which grains regularly travel from cold, water-rich regions to the warm inner part. This drift affects composition, grain size, morphology, and water content as grains experience ever higher temperatures. In this study we tempered chondritic dust under vacuum up to 1400 K. Afterwards, we measured the splitting tensile strength of millimetre-sized dust aggregates. The deduced effective surface energy starts out as γe = 0.07 J m−2. This value is dominated by abundant iron-oxides as measured by Mössbauer spectroscopy. Up to 1250 K, γe continuously decreases by up to a factor five. Olivines dominate at higher temperature. Beyond 1300 K dust grains significantly grow in size. The γe no longer decreases but the large grain size restricts the capability of growing aggregates. Beyond 1400 K aggregation is no longer possible. Overall, under the conditions probed, the stability of dust pebbles would decrease towards the star. In view of a minimum aggregate size required to trigger drag instabilities it becomes increasingly harder to seed planetesimal formation closer to a star.

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Section: Mössbauer Spectroscopy Measurementsmentioning

confidence: 99%

Drifting inwards in protoplanetary discs I Sticking of chondritic dust at increasing temperatures

Bogdan

Pillich

Landers

et al. 2020

A&A

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“…The magnetic phase transition leads to an increase of the absorption area compared to the paramagnetic region, due to a splitting of the resonance lines. 53,54 The obtained Debye temperatures are shown in Tab. I.…”

Section: Magneto-structural Phase Transitionmentioning

confidence: 99%

“…δ is a measure for the electron density at the Fe-nucleus. The temperature dependence of the isomer shift, 53 which is shown in Fig. 11, is a sum of the temperature-independent chemical shift δ C and a temperature dependent contri-bution δ R (T ) due to the second-order Doppler shift…”

Section: Magneto-structural Phase Transitionmentioning

confidence: 99%

Microscopic coexistence of superconductivity and magnetism in Ca1-xNaxFe2As2

Materne¹,

Kamusella²,

Sarkar³

et al. 2015

Preprint

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We present a detailed investigation of the magnetic and superconducting properties of Ca1−xNaxFe2As2 single crystals with x = 0.00, 0.35, 0.50, and 0.67 by means of the local probe techniques Mössbauer spectroscopy and muon spin relaxation experiments. With increasing Nasubstitution level, the magnetic order parameter as well as the magneto-structural phase transition are suppressed. For x = 0.50 we find a microscopic coexistence of magnetic and superconducting phases accompanied by a reduction of the magnetic order parameter below the superconducting transition temperature Tc. A systematic comparison with other 122 pnictides reveals a square-root correlation between the reduction of the magnetic order parameter and the ratio of the transition temperatures, Tc/TN , which can be understood in the framework of a Landau theory. In the optimally doped sample with Tc ≈ 34 K, diluted magnetism is found and the temperature dependence of the penetration depth and superfluid density are obtained, proving the presence of two superconducting s-wave gaps.

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“…Longer (shorter) lifetimes than indicated lead, according to the Heisenberg uncertainty principle, to too narrow (broad) emission and absorption lines, which no longer effectively overlap. Even for samples of Mössbauer nuclei, the probability of recoilless absorption and emission is mostly less than one, and can be approximated in the Debye model [35],…”

Section: Collective Effectsmentioning

confidence: 99%

Cooperative effects in nuclear excitation with coherent x-ray light

2012

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The interaction between super-intense coherent x-ray light and nuclei is studied theoretically. One of the main difficulties in driving nuclear transitions arises from the very narrow nuclear excited state widths, which limit the coupling between lasers and nuclei. In the context of direct laser-nucleus interaction, we consider the nuclear width broadening that occurs when in solid targets, when the excitation caused by a single photon is shared by a large number of nuclei, forming a collective excited state. Our results show that cooperative effects mostly contribute with a modest increase to the nuclear excited state population except in the case of 57 Fe, where the enhancement can reach almost two orders of magnitude. Additionally, an update is given of previous estimates of the nuclear excited state population and signal photons for x-ray lasers interacting with solid-state and ion beam nuclear targets taking into account the experimental advances of x-ray coherent light sources. The presented values are an improvement by orders of magnitude and are encouraging as to the future prospects of nuclear quantum optics.

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Grundlagen und Anwendungen der Mössbauerspektroskopie

Cited by 41 publications

References 0 publications

Drifting inwards in protoplanetary discs I Sticking of chondritic dust at increasing temperatures

Drifting inwards in protoplanetary discs I Sticking of chondritic dust at increasing temperatures

Microscopic coexistence of superconductivity and magnetism in Ca1-xNaxFe2As2

Cooperative effects in nuclear excitation with coherent x-ray light

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