Observation of Free Electron Cyclotron Resonance in NaAlSi3O8 Feldspar: Direct Determination of the Effective Electron Mass

Poolton, N.R.J.; Nicholls, J.E.; Bøtter‐Jensen, L.; Smith, Graham; Riedi, P. C.

doi:10.1002/1521-3951(200106)225:2<467::aid-pssb467>3.0.co;2-3

Cited by 13 publications

(7 citation statements)

References 27 publications

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“…to be applicable for feldspars, Poolton et al (2002b) predicted a ground state energy (n = 1) of 1.97 eV from the conduction band edge and a transition from the ground state to the excited state (1s -> 2p optical transition) of 1.48 ± 0.04 eV, both of which are based on the same variables for the effective electron mass (m e * = (0.79 ± 0.02)m e , Poolton et al, 2001) and the relative permittivity of the material of ε r = 2.33 (for Na-feldspar end member, Keller, 1966). ) represents the trap depth (E t ).…”

Section: Variations In Excitation Spectra Of Alkali Feldsparsmentioning

confidence: 99%

Site-selective characterisation of electron trapping centres in relation to chemistry, structural state and mineral phases present in single crystal alkali feldspars

Riedesel¹,

Kumar²,

Duller³

et al. 2021

J. Phys. D: Appl. Phys.

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Feldspars are ubiquitous natural dosimeters widely used in luminescence dating. Despite decades of research, the lattice defects as well as the mechanisms involved in luminescence production in feldspars remain poorly understood. The recently developed method of infrared-photoluminescence (IRPL) excitation-emission spectroscopy has revealed the presence of two electron trapping centres emitting IRPL at 1.3 eV and 1.41 eV (IRPL 1.3 and IRPL 1.41 centres), and it enables detailed investigations into the ground and excited state energies of these centres.Here we make measurements of a range of single crystal alkali feldspars to understand the effects of feldspar chemical composition, crystal structure and framework disorder on the physical characteristics of IRPL 1.3 and IRPL 1.41 electron trapping centres. Measurements of our sample suite reveals IRPL and IR-RL emissions at 1.41 eV, 1.3 eV and, for the first time, at 1.2 eV. Our results show that whilst the IRPL 1.3 trapping centre is unaffected by the M site cation occupancy, the presence of IRPL 1.41 trapping centres seems to be linked to the presence of K + ions on M sites. However, no clear trends in IRPL and IR-RL emission energies and signal intensities with chemical composition of the 2 samples were found. Exploring the effect of framework disorder on IRPL 1.3 and IRPL 1.41 emissions revealed no significant changes to IRPL and IR-RL emission energies or ground state energies of the trapping centres, suggesting that the corresponding defects are not located on bridging O ions.Variations in ground state energies across the whole sample suite range from 2.04 eV to 2.20 eV for the IRPL 1.3 centre and from 2.16 eV to 2.46 eV for the IRPL 1.41 centre. Variations in trap depth seem to be driven by other factors than sample chemistry, degree of Al 3+ disorder and number of phases present in a single crystal feldspar. Interestingly, the IR resonance peak is invariant between samples.Regarding the use of IRPL in luminescence dating, we show that optical resetting differs for the three different emissions, with the emission at ~1.41 eV not being reset in some samples even after 18 hours of solar bleaching. orthoclase, Short (2004) inferred the electron trap in that sample to be located at a tetrahedral site on the framework. More recently, based on infrared photoluminescence (IRPL), Kumar et al. (2018Kumar et al. ( , 2020a proposed that the defect acting as an electron trapping centre is located in two different lattice environments within the feldspar lattice resulting in two different types of trapping centres (referred to as the IRPL 1.41 and IRPL 1.3 centre, where the subscript denotes the emission energy in eV). The observations by Erfurt (2003) and Short ( 2004) are only based on single alkali feldspar samples and the samples used by Kumar et al. (2018Kumar et al. ( , 2020a were primarily feldspars separated from sediments which therefore inevitably consisted of grains with a range of chemical compositions. Kumar et al. (2020a) also presented results for two sing...

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Section: Variations In Excitation Spectra Of Alkali Feldsparsmentioning

confidence: 99%

Site-selective characterisation of electron trapping centres in relation to chemistry, structural state and mineral phases present in single crystal alkali feldspars

Riedesel¹,

Kumar²,

Duller³

et al. 2021

J. Phys. D: Appl. Phys.

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“…Finally, as noted above, the common α-quartz is an indirect band-gap material. However, recent measurements have been made (using optically detected cyclotron resonance) of the effective electron mass in NaAlSi 3 O 8 feldspar (Poolton et al 2001): the measured value of m * e = 0.79m e is slightly higher than that of quartz (at m * e ∼ 0.5m e ) and indicates probable poor mobility of electrons in the material. More significantly, the cyclotron resonance was found to be essentially isotropic with crystal orientation, strongly indicating that Na-feldspar might be a direct-gap material, or at least have a much smaller variation of the conduction band, in k-space, compared with quartz.…”

Section: Physical and Electronic Properties Of Feldspar: A Brief Over...mentioning

confidence: 99%

“…The set of feldspar samples used in this study were loaned from the mineral collection of the University of Copenhagen, and have been subject to extensive previous investigations regarding their compositional, structural, defect and optical properties (Poolton et al 1995a(Poolton et al , b, 1996(Poolton et al , 2001(Poolton et al , 2003. They were chosen to represent a broad range of compositions across the two principal series of the ternary system.…”

Section: Samplesmentioning

confidence: 99%

Luminescence excitation characteristics of Ca, Na and K-aluminosilicates (feldspars) in the stimulation range 5–40 eV: determination of the band-gap energies

Malins¹,

Poolton²,

Quinn³

et al. 2004

J. Phys. D: Appl. Phys.

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The first comprehensive survey of band-edge features in the ternary group of naturally occurring aluminosilicates (the feldspars) is presented. Synchrotron-based luminescence excitation of KAlSi 3 O 8 , NaAlSi 3 O 8 and CaAl 2 Si 2 O 8 allows the measurement of the evolution of the band-gap across the system, which, at 8 K, is found to vary from 7.86 eV in NaAlSi 3 O 8 to 7.7 eV and 7.62 eV in KAlSi 3 O 8 and CaAl 2 Si 2 O 8 , respectively: the band-gap energies are typically 0.1 eV smaller at 300 K. In comparison with measurements made on natural and synthetic hydrothermal α-quartz, where both the direct and indirect band-gap structures are distinctly observable, no significant post-edge band structure is discernable in the feldspars. In Ca-rich material, the luminescence is attenuated by more than two orders of magnitude for excitation energies up to 3 eV above the band-gap, partly supporting the proposition (derived from previous cyclotron resonance experiments) that the bands are simply parabolic and that the materials may be direct band-gap insulators. The luminescence excitation experiments also allow an initial survey to be made of sub-band-gap features in the materials, including low mobility, temperature sensitive band-tail states and mid-gap defects.

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“…(2) The dose dependence of line position is the manifestation of increasing number of oxygen hole centers with dose. (3) The observation of the g eff = 2.54 line has implications for the reported cyclotron resonance in potassium feldspars [20] and will be dealt with elsewhere.…”

Section: Resultsmentioning

confidence: 96%

An unusual radiation dose dependent EPR line atg_eff= 2.54 in feldspars: possible evidence of Fe³⁺O²⁻↔ Fe²⁺O⁻and exchange coupled Fe³⁺–Fe²⁺–nO⁻

Sastry

Nagar

Bhushan

et al. 2007

J. Phys.: Condens. Matter

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We report electron paramagnetic resonance (EPR) results on natural feldspar grains extracted from sediment samples of three widely different source regions. The XRD analysis indicated that the samples had albite, microcline and Ca/Ba–orthoclase as the major constituents. The EPR spectrum of all the samples exhibited an intense line around geff = 4.3. This is characteristic of Fe3+ with a zero field splitting that is significantly larger than the microwave quantum. More interesting was the presence of a strong EPR signal in the region of geff = 2.54–2.7. On irradiation with gamma rays the position of the line shifted to higher magnetic field. The possible origin of this line and its unusual behavior with dose is explained as being due to the interaction of a hopping ‘hole’ on oxygen with iron centers. The possibilities considered include (1) the valence fluctuation of an Fe3+ center at a tetrahedral site, (2) oscillation of FeO4− between two resonant forms, Fe2+O− and Fe3+O2−, and (3) exchange coupling between Fe3+, Fe2+ and O−. The concentration of the latter is dose dependent and, consequently, it results in the observed dose dependent line shift.

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Observation of Free Electron Cyclotron Resonance in NaAlSi3O8 Feldspar: Direct Determination of the Effective Electron Mass

Cited by 13 publications

References 27 publications

Site-selective characterisation of electron trapping centres in relation to chemistry, structural state and mineral phases present in single crystal alkali feldspars

Site-selective characterisation of electron trapping centres in relation to chemistry, structural state and mineral phases present in single crystal alkali feldspars

Luminescence excitation characteristics of Ca, Na and K-aluminosilicates (feldspars) in the stimulation range 5–40 eV: determination of the band-gap energies

An unusual radiation dose dependent EPR line atg_eff= 2.54 in feldspars: possible evidence of Fe³⁺O²⁻↔ Fe²⁺O⁻and exchange coupled Fe³⁺–Fe²⁺–nO⁻

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Observation of Free Electron Cyclotron Resonance in NaAlSi3O8 Feldspar: Direct Determination of the Effective Electron Mass

Cited by 13 publications

References 27 publications

Site-selective characterisation of electron trapping centres in relation to chemistry, structural state and mineral phases present in single crystal alkali feldspars

Site-selective characterisation of electron trapping centres in relation to chemistry, structural state and mineral phases present in single crystal alkali feldspars

Luminescence excitation characteristics of Ca, Na and K-aluminosilicates (feldspars) in the stimulation range 5–40 eV: determination of the band-gap energies

An unusual radiation dose dependent EPR line atgeff= 2.54 in feldspars: possible evidence of Fe3+O2−↔ Fe2+O−and exchange coupled Fe3+–Fe2+–nO−

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An unusual radiation dose dependent EPR line atg_eff= 2.54 in feldspars: possible evidence of Fe³⁺O²⁻↔ Fe²⁺O⁻and exchange coupled Fe³⁺–Fe²⁺–nO⁻