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We report observations of crystal defect induced modifications in the laser-excited Er3+ photoluminescence spectra of single-crystal Er2O3 thin films. These include marked enhancement of transition intensities known to be weak or nonexistent in as-grown samples. In this Letter, we examine the temperature and defect density dependence of the measurements and suggest photophysical processes that may account for these unexpected results. 

A theoretical investigation is conducted on the s- and p-wave elastic scatterings of positronium by a lithium ion Li+ with the scattering energy below 1.41 eV, corresponding to the threshold of the e+-Li channel. The confined variational method is applied to serve as the theoretical framework for this study. To accurately account for correlations between involved particles, explicitly correlated Gaussians are employed as basis functions, which are optimized through a hybrid approach combining stochastic variational and energy-gradient-based methods. Additionally, a straightforward yet effective algorithm is developed for the automatic adjustment of confining potentials. The s-wave zero-energy pickoff annihilation parameter 1Zeff,0 is accurately determined to be 0.126 ± 0.002, which yields an enhancement factor of 1.88 compared with the value 0.067 obtained using the fixed-core stochastic variational method [Phys. Rev. A 65, 034709 (2002)]. Finally, a broad p-wave resonance structure is predicted at the incident energy of approximately 0.27 eV, with the annihilation parameter 1Zeff,1 at the resonance center estimated to be around 0.034. 

The highly infectious disease COVID-19 caused by the Betacoronavirus SARS-CoV-2 poses a severe threat to humanity, and demands for redirection of scientific efforts and criteria to organized research projects. The international Covid19-NMR consortium seeks to provide such new approaches by gathering scientific expertise worldwide. In particular, making available viral proteins and RNAs will pave the way to understanding the SARS-CoV-2 molecular components in detail. The research in Covid19-NMR and the resources provided through the consortium are fully disclosed to accelerate access and exploitation. NMR investigations of the viral molecular components are designated to provide the essential basis for further work, including macromolecular interaction studies and high-throughput drug screening. Here, we present the extensive catalogue of a holistic SARS-CoV-2 protein preparation approach based on the consortium’s collective efforts. We provide protocols for the large-scale production of more than 80% of all SARS-CoV-2 proteins or essential parts of them. Several of the proteins were produced in more than one laboratory, demonstrating the high interoperability between NMR groups worldwide. For the majority of proteins, we can produce isotope-labeled samples of HSQC-grade. Together with several NMR-chemical shift assignments made publicly available on covid19-nmr.com, we here provide highly valuable resources for the production of SARS-CoV-2 proteins in isotope labeled form.