Structure of SnF2-SnO-P2O5 Glasses

AbstractLow melting point glasses, specifically tin fluorophosphates, have recently received attention as a successful host matrix to rare earth metals to be used in photon conversion for solar cell applications. We have used high resolution X-ray photoelectron spectroscopy and Raman microscopy to investigate the structure of 50SnF2-20SnO-30P2O5 glass. To compliment this experimental study density functional theory was used to predict Raman spectra. The O 1s X-ray photoelectron spectra indicate a high non-bridging to bridging oxygen ratio, a sign of relatively high durability needed for this glass to be applied to solar energy. The experimental results are in good agreement with theoretical calculations

A study of the breakdown of the quasi-static approximation at high densities and its effect on the helium-like K ALPHA complex of nickel, iron, and calcium

The General Spectral Modeling (GSM) code employs the quasi-static approximation, a standard, low-density methodology that assumes the ionization balance is separable from a determination of the excited-state populations that give rise to the spectra. GSM also allows for some states to be treated only as contributions to effective rates. While these two approximations are known to be valid at low densities, this work investigates using such methods to model high-density, non-LTE emission spectra and determines at what point the approximations break down by comparing to spectra produced by the LANL code ATOMIC which makes no such approximations. As both approximations are used by other astrophysical and low-density modeling codes, the results should be of broad interest. He-like K$\alpha$ emission spectra are presented for Ni, Fe, and Ca, in order to gauge the effect of both approximations employed in GSM. This work confirms that at and above the temperature of maximum abundance of the He-like ionization stage, the range of validity for both approximations is sufficient for modeling the low- and moderate-density regimes one typically finds in astrophysical and magnetically confined fusion plasmas. However, a breakdown does occur for high densities; we obtain quantitative limits that are significantly higher than previous works. This work demonstrates that, while the range of validity for both approximations is sufficient to predict the density-dependent quenching of the z line, the approximations break down at higher densities. Thus these approximations should be used with greater care when modeling high-density plasmas such as those found in inertial confinement fusion and electromagnetic pinch devices.Comment: Accepted by Physical Review A (http://pra.aps.org/). 11 pages + LANL cover, 5 figures. Will update citation information as it becomes available. Abbreviated abstract is listed her

Results from the Eclipse of August 21, 2017

No abstract availabl

Parametrizace fotosvětlání a fototmavnutí in-situ kinetik v napařených vrstvách GeSe2

Thermally evaporated chalcogenide glass thin films are known to be highly photosensitive revealing both metastable and transient photoinduced changes of optical transmission at the fundamental absorption edge region. In-situ kinetics of metastable photobleaching and transient photodarkening as well as following light-off relaxations for as-deposited GeSe2 thin films were studied and fitted with the stretched exponential function. Dependences of kinetic parameters beta and tau a on film thickness, temperature, sample prehistory and wavelength of light irradiation were analyzed. The obtained results were discussed within current approaches to mechanisms of photoinduced kinetic phenomena and structural relaxation in glasses.Vakuově napařené tenké vrstvy chalkogenidových skel jsou známé pro svoji vysokou fotocitlivost odhalující metastabilní a přechodné fotoindukované změny optické propustnosti v regionu fundamentální absorpční hrany. Byly studovány a fitovány n-situ kinetiky metastabilního fotosvětlání a přechodného fototmavnutí čerstvě deponovaných vrstev GeSe2, jakožto i relaxace při vypnutí zdroje expozice. Byla analyzována závislost parametrů kinetiky beta a tau na tloušťce, teplotě, historii vzorku a vlnové délce použitého záření. Získané výsledky byly diskutovány v rámci současných přístupů k mechanismům fotoindukovaných jevů a strukturální relaxace ve sklech

Foto-odezva anorganicko-organických tenkovrstevnatých kompozitů na bázi chalkogenidových skel

Spin coated chalcogenide thin films have different structural and chemical properties than the films obtained by traditional methods such as thermal evaporation or sputtering. The solution-based method provides lower sensitivity of glass matrix to the influence of bandgap and superbandgap light. This property is very useful for non-linear optical applications based on high transparency of these materials in infrared spectral region. Arsenic selenide spin coated thin films were obtained by chemical dissolution of bulk glasses in ethylenediamine. The influence of preparation conditions, especially the annealing temperatures at the final stage of thin films synthesis, on in-situ kinetics of photodarkening (bleaching) at various energies and intensities of UV-VIS light was studied. It was found that at certain annealing conditions only transient photoinduced effects can be obtained by eliminating metastable kinetic component. Mechanisms of the photoinduced effects are discussed based on the parameters of relaxation functions.Spin-coatingem deponované chalkogenidové tenké vrstvy mají rozdílnou strukturu a chemické vlastnosti než vrstvy získané tradičními metodami jako je vakuové napařování nebo naprašování. Roztokové depoziční metody poskytují nižší citlivost skelné matrice vůči účinku světla o bandgapových a superbandgapových energií. Tato vlastnost je velice užitečná pro nelineární optické aplikace založené na vysoké propustnosti těchto materiálů v IČ oblasti spektra. Tenké vrstvy selenidu arsenitého byly získány rozpouštěním objemového skla v etylendiaminu. Vliv podmínek během přípravy, zvláště pak teplota temperace v posledních fází přípravy vrstev, na in-situ kinetiky fototmavnutí (světlání) při různých energiích a intenzitách UV-VIS táření byly studovány v této práci. Bylo zjištěno, že pouze při určitých podmínkách temperace lze získat vratné fotoindukované změny díky eliminaci metastabilní kinetické komponenty. Mechanismus fotoindukovaných jevů je dále diskutován na základě parametrů relaxačních funkcí