Recombination Radiation in the Diamond

The quest for making a triplet positronium (Ps) Bose–Einstein condensate confined in a micron-sized cavity in a material such as porous silica faces at least three interrelated problems: (1) About $$10^7$$ 10 7 spin polarized Ps atoms must be injected into a small cavity within a porous solid material without vaporizing it. (2) It is known that Ps atoms confined in 30–100 nm diameter cavities in porous silica do not remain in the gas phase, but become stuck to the cavity walls at room temperature (Cooper et al., Phys. Rev. B 97:205302, 2018). (3) Cooling a gas of Ps atoms to cryogenic temperatures by energy exchange with the walls would be a very slow process (Saito and Hyodo, in: Surko, Gianturco (eds) New Directions in Antimatter Chemistry and Physics, Springer Dordrecht, Netherlands, 2001) because of the relatively low collision rate with the walls and the large mismatch between the masses of the Ps and the wall atoms. A possible solution of these difficulties is presented, based on cooling the implanted positrons in an isotopically pure diamond single crystal target, subsequent saturating of the wall Ps coverage so that a substantial portion of the Ps will be in the gaseous state, and thermalizing the gas-phase Ps via collisions with the low effective mass wall Ps. A design process for the target material is outlined as well, including preliminary results in porous cavity fabrication using focused ion beam milling. Graphical abstract

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“…Thus, the positrons should efficiently reach the hollow cavity depicted in Fig. 2b and fill it with Ps [49,50].…”

Section: Positron Mobility In Diamondmentioning

confidence: 99%

Conditions for obtaining positronium Bose–Einstein condensation in a micron-sized cavity

et al. 2022

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“…The argon rectification hypothesis postulates that high temperature inside the bubble determines the dissociation of molecular oxygen and nitrogen; the reactive species formed in the process are, then, irreversibly transferred to the liquid medium, leaving inside the bubble only non-reactive noble gases (such as argon, which is present in the air at a concentration of 1%); the latter are, then, responsible for bubble stability and electromagnetic emission [ 28 , 30 , 31 ]. Recombination radiation, finally, is the light radiation emitted when a free electron is captured by a ion [ 32 ].…”

Section: Sonodynamic Therapy: a New Asset For Non-invasive Glioma mentioning

confidence: 99%

Sonodynamic Therapy for the Treatment of Intracranial Gliomas

D’Ammando

Raspagliesi

Gionso

et al. 2021

JCM

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High-grade gliomas are the most common and aggressive malignant primary brain tumors. Current therapeutic schemes include a combination of surgical resection, radiotherapy and chemotherapy; even if major advances have been achieved in Progression Free Survival and Overall Survival for patients harboring high-grade gliomas, prognosis still remains poor; hence, new therapeutic options for malignant gliomas are currently researched. Sonodynamic Therapy (SDT) has proven to be a promising treatment combining the effects of low-intensity ultrasound waves with various sound-sensitive compounds, whose activation leads to increased immunogenicity of tumor cells, increased apoptotic rates and decreased angiogenetic potential. In addition, this therapeutic technique only exerts its cytotoxic effects on tumor cells, while both ultrasound waves and sensitizing compound are non-toxic per se. This review summarizes the present knowledge regarding mechanisms of action of SDT and currently available sonosensitizers and focuses on the preclinical and clinical studies that have investigated its efficacy on malignant gliomas. To date, preclinical studies implying various sonosensitizers and different treatment protocols all seem to confirm the anti-tumoral properties of SDT, while first clinical trials will soon start recruiting patients. Accordingly, it is crucial to conduct further investigations regarding the clinical applications of SDT as a therapeutic option in the management of intracranial gliomas.

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“…The CL recombination A-band is superimposed on the intracenter luminescence of the neutral vacancy, V(GR1), nitrogen vacancy, NV (575 nm), N 2 V (H3), N 3 V (N3), N 4 V 2 (H4) centers, and the broad structureless band of B' centers (platelets) [24]. The mechanisms of energy transfer to the PL centers during electron excitation in diamond have been poorly investigated [25,26]. The apparent zoning of crystals is mostly caused by nonuniform distribution of the A-band intensity as well as the N3 and H3 systems [27].…”

Section: Introductionmentioning

confidence: 99%

Cathodoluminescence of Diamond: Features of Visualization

et al. 2021

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Zonal and sectorial heterogeneities in natural diamonds provide information on the growth conditions and post-growth changes. Cathodoluminescence (CL) microscopy revealed these heterogeneities in a very detailed manner with high spatial resolution. In this study, factors affecting the CL images of two natural diamonds were analyzed and the results of cathodoluminescence studies in steady-state (SS-CL) and scanning modes were compared. SS-CL was observed using an optical microscope, and scanning mode was evaluated via SEM (SEM-CL). It was demonstrated that the relative brightness of the <111> and <100> growth sectors in diamond crystals depends on the nature of defects in them and on the method of image detection (steady-state/scanning versus color/panchromatic). The differences between SS-CL and SEM-CL images can be attributed to the kinetics of luminescence and spectral sensitivity of the detectors. It was established that the nature of lattice defects around small inclusions can be changed (e.g., the intensity of blue luminescence from nitrogen-vacancy defects (N3V) decreases due to their transformation into nitrogen–hydrogen defects (N3VH). The hydrogen disproportion between the sectors is caused by different growth mechanisms. Hydrogen atoms in the diamond matrix can affect the kinetics of transformation of the defects by transforming a part of N3V to N3VH.

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Recombination Radiation in the Diamond

Cited by 5 publications

References 36 publications

Conditions for obtaining positronium Bose–Einstein condensation in a micron-sized cavity

Conditions for obtaining positronium Bose–Einstein condensation in a micron-sized cavity

Sonodynamic Therapy for the Treatment of Intracranial Gliomas

Cathodoluminescence of Diamond: Features of Visualization

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