Towards direct measurement of electrons in metastable states in K-feldspar: Do infrared-photoluminescence and radioluminescence probe the same trap?

Kumar, Raju; Kook, Myungho; Murray, Andrew; Jain, Mayank

doi:10.1016/j.radmeas.2018.06.018

Cited by 38 publications

(42 citation statements)

References 27 publications

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“…In each excitation mode, the emission spectrum in the NIR range (850-1100 nm) consists of a broad peak centered at ~ 900 nm. For the XEOL and PL measurements on the same sample (R47), Kumar et al 18 showed that this broad peak splits into two peaks centered at ~ 880 nm (1.41 eV) and ~ 955 nm (1.30 eV) at a low temperature of 7 K. CL and XEOL mechanisms are similar in terms of ionization and trapping; the only difference is the interaction volume of the crystal. In the case of CL, we are biased by the near-surface traps as the penetration depth of 20 keV electrons is only about 4 µm in feldspar 39 .…”

Section: Cathodoluminescence (Cl) X-ray Excited Optical Luminescencementioning

confidence: 99%

Site-selective mapping of metastable states using electron-beam induced luminescence microscopy

Kumar

Martin

Poelman

et al. 2020

Sci Rep

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Metastable states created by electron or hole capture in crystal defects are widely used in dosimetry and photonic applications. Feldspar, the most abundant mineral in the Earth’s crust (> 50%), generates metastable states with lifetimes of millions of years upon exposure to ionizing radiation. Although feldspar is widely used in dosimetry and geochronometry, the creation of metastable states and charge transfer across them is poorly understood. Understanding such phenomena requires next-generation methods based on high-resolution, site-selective probing of the metastable states. Recent studies using site-selective techniques such as photoluminescence (PL), and radioluminescence (RL) at 7 K have revealed that feldspar exhibits two near-infrared (NIR) emission bands peaking at 880 nm and 955 nm, which are believed to arise from the principal electron-trapping states. Here, we map for the first time the electron-trapping states in potassium-rich feldspar using spectrally-resolved cathodoluminescence microscopy at a spatial resolution of ~ 6 to 22 µm. Each pixel probed by a scanning electron microscope provides us a cathodoluminescence spectrum (SEM-CL) in the range 600–1000 nm, and elemental data from energy-dispersive x-ray (EDX) spectroscopy. We conclude that the two NIR emissions are spatially variable and, therefore, originate from different sites. This conclusion contradicts the existing model that the two emissions arise from two different excited states of a principal trap. Moreover, we are able to link the individual NIR emission peaks with the geochemical variations (K, Na and Fe concentration), and propose a model that explains the quenching of the NIR emission by Fe4+. Our study contributes to an improved understanding of charge storage in feldspathic minerals, with implications for developing sub-single grain (micrometer scale) measurement techniques in radiation dosimetry.

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Section: Cathodoluminescence (Cl) X-ray Excited Optical Luminescencementioning

confidence: 99%

Site-selective mapping of metastable states using electron-beam induced luminescence microscopy

Kumar

Martin

Poelman

et al. 2020

Sci Rep

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“…The experimental details are described in the 'Materials and methods' section. In brief, we measure both the dose-dependent Stokes-shifted IRPL emissions in feldspar (~ 880 and ~ 955 nm) in all the investigations 16 . Throughout the text, the IRPL (955 nm) and IRPL (880 nm) emissions are denoted as IRPL 955 and IRPL 880 , respectively.…”

Section: Current Understanding Of Stimulated-luminescence Emission Inmentioning

confidence: 99%

“…Throughout the text, the IRPL (955 nm) and IRPL (880 nm) emissions are denoted as IRPL 955 and IRPL 880 , respectively. Kumar et al 16,37 demonstrated that these signals do not represent the two excited states of the same defect site but instead two different sites; the respective (unknown) principal traps that give rise to these signals are referred to as the 880 or 955 nm (emission) centres.…”

Section: Current Understanding Of Stimulated-luminescence Emission Inmentioning

confidence: 99%

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A novel coupled RPL/OSL system to understand the dynamics of the metastable states

Jain

Kumar

Kook

2020

Sci Rep

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Metastable states form by charge (electron and hole) capture in defects in a solid. They play an important role in dosimetry, information storage, and many medical and industrial applications of photonics. Despite many decades of research, the exact mechanisms resulting in luminescence signals such as optically/thermally stimulated luminescence (OSL or TL) or long persistent luminescence through charge transfer across the metastable states remain poorly understood. Our lack of understanding owes to the fact that such luminescence signals arise from a convolution of several steps such as charge (de)trapping, transport and recombination, which are not possible to track individually. Here we present a novel coupled RPL(radio-photoluminescence)/OSL system based on an electron trap in a ubiquitous, natural, geophotonic mineral called feldspar (aluminosilicate). RPL/OSL allows understanding the dynamics of the trapped electrons and trapped holes individually. We elucidate for the first time trap distribution, thermal eviction, and radiation-induced growth of trapped electron and holes. The new methods and insights provided here are crucial for next generation model-based applications of luminescence dating in Earth and environmental sciences, e.g. thermochronometry and photochronometry.

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“…Luminescent signals that have not yet been used for tephra dating include infrared radiofluorescence (IR-RF) (Trautmann et al, 1998(Trautmann et al, , 1999Erfurt and Krbetschek, 2003;Frouin et al, 2017) and infrared photoluminescence (IR-PL; Erfurt, 2003;Prasad et al, 2017) of K-feldspar. For these methods, the signal is recorded during ionizing irradiation (IR-RF) or during stimulation with IR radiation, respectively, but it is assumed that the sampled electron trap is the same (Kumar et al, 2018). Although both methods require further basic research (see Buylaert et al, 2012b), the signals do not seem to be affected by anomalous fading, and their comparatively large saturation doses should allow reliable dating of tephra (far) beyond the last glacial cycle.…”

Section: Discussionmentioning

confidence: 99%

Direct and indirect luminescence dating of tephra: A review

Bösken

Schmidt

2019

J Quaternary Science

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In Quaternary studies, tephras are widely used as marker horizons to correlate geological deposits. Therefore, accurate and precise dating is crucial. Among radiometric dating techniques, luminescence dating has the potential to date tephra directly using glass shards, volcanic minerals that formed during the eruption or mineral fragments that originate from the shattered country rock. Moreover, sediments that frame the tephra can be dated to attain an indirect age bracket. A review of numerous luminescence dating studies highlights the method's potential and challenges. While reliable direct dating of volcanic quartz and feldspar as a component in tephra is still methodically difficult mainly due to thermal and athermal signal instability, red thermoluminescence of volcanic quartz and the far-red emission of volcanic feldspar have been used successfully. Furthermore, the dating of xenolithic quartz within tephra shows great potential. Numerous studies date tephra successfully indirectly. Dating surrounding sediments is generally straightforward as long as samples are not taken too close to the tephra horizons. Here, issues arise from the occurrence of glass shards within the sediments or unreliable determination of dose rates. This includes relocation of radioelements, mixing of tephra into the sediment and disregarding different dose rates of adjacent material.

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Towards direct measurement of electrons in metastable states in K-feldspar: Do infrared-photoluminescence and radioluminescence probe the same trap?

Cited by 38 publications

References 27 publications

Site-selective mapping of metastable states using electron-beam induced luminescence microscopy

Site-selective mapping of metastable states using electron-beam induced luminescence microscopy

A novel coupled RPL/OSL system to understand the dynamics of the metastable states

Direct and indirect luminescence dating of tephra: A review

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