Understanding the mineralogy of the Moon is key to viable mining and mineral processing necessary for the utilization of resources on the lunar surface. As on Earth, the minerals present in a resource can have drastically different physical and chemical properties, and require varying processing protocols to extract useful materials. The mineralogical and chemical complexity of lunar material requires more detailed analysis than simple observation of the elemental composition for detailed scientific understanding, or successful resource extraction. However, traditional non-contact sensing suffers from either low spatial resolution, or the inability to collect data fast enough to enable real-time decision making. Real-time data facilitates selective mining of target minerals of interest, and the optimization of mineral feeds consistent, high yields of extracted resources. Fluorescence analysis can obtain detailed mineralogical information at a high spatial resolution, while still being able to analyze bulk areas at speeds rapid enough such that precise mining or mineral processing control operations can occur. Useful fluorescence from minerals does occur, especially in the near-infrared (NIR), with these 'novel fluorescence' peaks standing out in an otherwise low-background emission waveband range, and are additionally enhanced at cold temperatures. This is demonstrated through the detection of NIR fluorescence discovered from specific minerals important for metal, oxygen, and water extraction on the lunar surface. The practical implementation of sensing devices utilizing this novel fluorescence is discussed, showing that simple and reliable systems can be designed which locate high-value lunar minerals in real-time with minimal data processing or deconvolution required.

Fluorine-based defect structures in calcium fluoride have previously been shown to emit visible-spectrum fluorescence when excited by UV light. This work shows the behaviour of a new fluorescence centre emitting in the near infrared at 1100-1200 nm when excited by visible light. This emission was most readily observed in natural fluorite samples, which have structural defects due to a long term exposure to environmental radiation, but was also induced in a synthetic calcium fluoride sample using intense UV light. Excitation of the near infrared emission reaches a maximum near the previously reported F-centre aggregate absorption peak. Emission is also "recharged" when excited by photons matching the fluorine interstitial migration energy. The measurement of this fluorescence could be used to monitor defects in optical grade fluorite caused by high power lasers and could also have applications in fluorite mineral detection during mining operations. Potential resetting of these optical defects is additionally discussed.

Large core soft glass fibers have been demonstrated to be promising candidates as intrinsic fiber sensors for radiation detection and dosimetry applications. Doping with rare earth ions enhanced their radiation sensitivity. SiO2-Al2O3-La2O3 (SAL) glasses offer easy fabrication of large core fibers with high rare earth concentration and higher mechanical strength than soft glasses. This paper evaluates the suitability of the SAL glass type for radiation dosimetry based on optically stimulated luminescence (OSL) via a comprehensive investigation of the spectroscopic and dosimetric properties of undoped and differently rare earth doped bulk SAL glass samples. Due to the low intensity of the rare earth luminescence peaks in the 250–400 nm OSL detection range, the OSL response for all the SAL glasses is not caused by the rare earth ions but by radiation-induced defects that act as intrinsic centers for the recombination of electrons and holes produced by the ionizing radiation, trapped in fabrication induced defect centers, and then released via stimulation with 470 nm light. The rare earth ions interfere with these processes involving intrinsic centers. This dosimetric behavior of highly rare earth doped SAL glasses suggests that enhancement of OSL response requires lower rare earth concentrations and/or longer wavelength OSL detection range.

Acetone and butanone were seen to emit blue light around 450 nm when excited in the green by a high intensity pulsed laser. The pathway of this anti-Stokes emission is believed to be multiphoton absorption followed by phosphorescence, with emission being observed in the samples at cryogenic temperatures below their melting point and not seen from either ketone in their cold liquid state. Given the widespread nature of these simple ketones in off-world bodies and their potential importance as an organic resource for Space Resource Utilization, signals which enable the identification and tracing of these materials are of use in applications from remote sensing and mapping to monitoring during extraction processes. While the excitation process has a low efficiency, the ability to use visible light for sensing of these targets has advantages over UV sources, such as the wider availability of high-powered lasers which could be utilized.

Fluorine can negatively interfere with leach and smelting processes during mineral processing. Real-time knowledge of the concentration and mineral hosts of fluorine in a mineral processing ore stream is important to protect process line equipment and product. Currently only offline methods of detection are available. Online sensors that determine specific fluorine-bearing mineral concentration in real-time would enable improved efficiency in processing decisions during mine production. Common excitation wavelengths used for fluorescence studies in minerals frequently provide signals that are not clearly host-specific, and hence of limited utility for mineral identification. We show that upconversion fluorescence, a process in which two or more photons are absorbed and one higher-energy photon is emitted, provides a more host-specific fluorescence output, minimizing spurious signals in complex environments and therefore greatly improving detection thresholds. Natural samples of fluorite (CaF2), a major fluorine host at many mine sites, have been analyzed by near-infrared excitation and have revealed upconversion fluorescence from rare earth inclusions. Upconversion fluorescence was detected in samples with rare earth concentrations as low as one part per million and is therefore considered a potential new sensing modality for real-time fluorite monitoring.

Erbium-doped ZBLAN (Er:ZBLAN) is a commonly used glass for mid-infrared fiber lasers. Quantifying the energy dynamics of the erbium ions is important for improving the performance of mid-infrared fiber lasers. Previous studies have found a discrepancy between the strength of inter-ion energy transfer measured in bulk Er:ZBLAN and the strength required to explain current fiber laser performance. We have measured the strength of the 4 I 13 / 2 + 4 I 13 / 2 → 4 I 15 / 2 + 4 I 9 / 2 energy transfer process directly in a range of fibers for the first time, to the best of our knowledge.

Understanding the upconversion pathways of a rare‐earth dopant is crucial to furthering the use of that material, either toward applications in imaging or elsewhere. This work outlines a new analysis approach that consists of using two synchronized widely‐tunable laser sources to explore the properties of upconverting materials. By examining sensitizer‐free rare‐earth nanoparticles based on a matrix of hexagonal sodium yttrium tetrafluoride (β‐NaYF 4 ) doped with praseodymium but no ytterbium sensitizer, a “non‐degenerate” two‐color upconversion fluorescence at a combined excitation of 1020–850 nm is shown. This insight demonstrates the ability of this technique to locate and interrogate novel upconversion pathways. The dopant level of the nanoparticles could be modified without altering other factors, such as the particle's shape or size, that would also change optical properties and this allows investigation of the dopant‐level dependency of the optical properties. The approach also allows exploration of the time delay domain between the arrival times of the two non‐degenerate excitation pulses, which allows modulation of the brightness from the visible light emissions. This work opens up the parameter space for the systematic synthesis and characterization of new materials with non‐degenerate upconversion emission.

Shorter-than-excitation-wavelength (STEW) optical emissions, where photons originating in a material have higher energies than those that created them, have in the past few decades become important in science and medicine, with applications ranging from improving the efficiency of solar cells to creating new lasers and performing background-free microscopy of biological samples. Assigning and predicting the origin of STEW emissions is critical for accelerating development and applications of new processes and materials. In this review, we examine the different processes underlying STEW emissions and outline pathways to identify them using readily available experimental techniques.

Shorter-than-excitation-wavelength (STEW) optical emissions, where photons originating in a material have higher energies than those that created them, have in the past few decades become important in science and medicine, with applications ranging from improving the efficiency of solar cells to creating new lasers and performing background-free microscopy of biological samples. Assigning and predicting the origin of STEW emissions is critical for accelerating development and applications of new processes and materials. In this review, we examine the different processes underlying STEW emissions and outline pathways to identify them using readily available experimental techniques.

In this study we present pulsed optically stimulated luminescence (OSL) measurements in quartz, directed towards the generation of information relevant to mechanisms studies. Our measurement program covers the pulsed OSL emitted from a number of laboratory-irradiated South Australian quartz samples shone across a wide temperature range. We reveal that although the response is dominated by a single exponential component, it also includes several faint slow components and a temperature-dependent step component. We find that the room temperature time constant of 40.9 +/- 0.2 mu s measured from the pulse fall exceeds the corresponding value of 39.9 +/- 0.2 mu s measured from the rise. Further, application of the Mott-Seitz formula across the temperature range has enabled a value of 0.694 +/- 0.004 eV to be derived for the activation energy associated with thermal quenching. Similar investigations yield a room temperature time constant of 1.60 +/- 0.02 ms and an activation energy of 1.1 +/- 0.05 eV for the strongest of the faint components. Regarding the step component, we find that it dominates the OSL as the temperature is increased. By applying linearly modulated OSL in the 300-450 degrees C high temperature region, we show that the step is generated even in the absence of applied ionising radiation.

Silica glasses doped with rare-earth ions are potential materials for optical fiber radiation detection and dosimetry applications. High sensitivity to radiation requires fibers with large cores that can be reliably fabricated using glass made in a novel process from the reactive powder sintering of silica. The luminescence and dosimetric properties of a range of rare earth-doped silica materials produced using this novel technique are reported here. Radioluminescence and optically stimulated luminescence (OSL) are the fundamental mechanisms enabling radiation detection in optical fibers. It was found that thermoluminescence, radioluminescence, and OSL are observed if the glass contains luminescent transitions in the detection wavelength range. Cerium- and thulium-doped silica glasses were found to be promising candidates for optical fiber dosimetry. Samples showed intense luminescence signals in response to both photo-stimulation and irradiation from alpha and beta sources. OSL results for cerium are three times larger than results for irradiated fluoride phosphate glasses previously tested for dosimetry use. Spectroscopic measurements indicate emission in the 300-500 nm region, suitable for detection with photomultiplier tubes.

We here introduce, for the first time, a topological carbon nitride (TCN) with built-in crystalline–amorphous phases.

Carbon nanodots (CDs) with size dependent fluorescence are synthesized from multi-walled carbon nanotubes (MWCNTs) under continuous flow in a vortex fluidic device (VFD) when irradiated by a pulsed laser with a wavelength of 1064 nm, without subsequent passivation procedures. The CDs have a relatively narrow size distribution averaging ca. 6 nm in diameter, and have low cytotoxicity and high colloidal stability with the highest emission intensity of the solution at 450 nm under a 345 nm excitation wavelength. Further downstream processing on the as-processed CDs revealed tunability of the emission from 450 nm to 325 nm.

We demonstrate the generation of metastable krypton in the long-lived 1s^{5} state using laser excitation. The atoms are excited through a two-photon absorption process into the 2p^{6} state using a pulsed optical parametric oscillator laser operating near 215 nm, after which the atoms decay quickly into the metastable state with a branching ratio of 75%. The interaction dynamics are modeled using density matrix formalism and, by combining this with experimental observations, we are able to calculate photoionization and two-photon absorption cross sections. When compared to traditional approaches to metastable production, this approach shows great potential for high-density metastable krypton production with minimal heating of the sample. Here, we show metastable production efficiencies of up to 2% per pulse. The new experimental results gained here, when combined with the density matrix model we have developed, suggest that fractional efficiencies up to 30% are possible under optimal conditions.

As part of an investigation into the mechanisms underlying optically stimulated luminescence (OSL) in quartz, we have shone a number of South Australian natural quartzes over a six day measurement period. During this time the OSL signal was recorded over ten decades in time and fell six to seven decades in luminescent intensity. In particular, we observe the presence of a number of steps that appear when the luminescence is displayed in log/log form. In exploring the underlying mechanism, we review both the standard energy band gap model for quartz OSL and the alternative defect pair model and find that the latter can be applied to explain the steps in terms of a nearest neighbour extension.

Amorphous carbon nitride (a‐CN) is a less‐explored but promising photocatalyst for hydrogen production. Despite an extended visible light absorption (EVLA) its low quantum efficiency (QE) for water photoreduction is a long standing problem. This implies that EVLA is not proportionally translated into collection of large amounts of photogenerated electrons. Minimizing the mismatch between light‐absorption and charge‐collection remains a scientific challenge. Here a sponge‐like hierarchical structure of a‐CN that addresses this apparent mismatch is reported. Combined experimental and finite difference time domain simulations demonstrate the ability of the a‐CN sponge to induce scattering for total internal light reflection that promotes localized charge carrier generation. Diffused reflectance and transient fluorescence decay studies show good agreement with simulations with a 40% enhanced light‐trapping and an ≈23 times longer electron lifetime in spongy a‐CN compared with that of the bulk material. The result is a new high benchmark for hydrogen production of 203.5 µmol h−1 with a QE of 6.1% at 420 nm in a reaction system of 10 vol% triethanolamine and 1 wt% Pt cocatalyst. The enhanced water photoreduction is a result of amenable photophysical and electrochemical attributes existing within the a‐CN sponge.

p. 5 Declaration p. 6 Acknowledgements p. 7

Seventeen domestic and scientific glass specimens were investigated for thermoluminescence (TL) properties suitable for application to retrospective population dosimetry. Usefulness for retrospective dosimetry was initially judged by the presence of well-defined TL glow peaks and the absence of irradiation-independent luminescence. Of particular interest were TL glow peaks having relatively low trap depths, to prevent significant natural dose accumulation. Minimum useful trap lifetimes would be in the order of weeks. Surveys were undertaken to observe the TL and optically stimulated luminescence (OSL) behaviour of each sample. Most samples showed identifiable TL, with Pyrex in particular, and samples from a jar, a lampshade, and opaque blue beads all showing well-defined TL glow peaks with sensitivities that were not significantly affected by prior irradiation and heating of the sample. Kinetic analysis of these samples showed that their TL emission originates from traps with suitable stability for retrospective dosimetry. It is concluded that, while some glass samples show promising results, the inherent variability of an amorphous substance such as glass means that the suitability of each sample must be determined on a case-by-case basis.