Search results for "states"
showing 10 items of 1532 documents
Determination of the number densities of argon metastables in argon-hydrogen plasma by absorption and self-absorption methods
2006
The number densities of Ar 3s23p54s levels have been measured by means of two methods: a self-absorption method with a mirror behind the discharge vessel and an absorption method with a high-frequency electrodeless discharge lamp. Concentrations ranging from 6 × 107–4 × 109 cm−3 were obtained for the Ar 3s23p54s levels, depending on the argon content (10–100% Ar) in Ar/H2 microwave plasma. The populations of various sublevels of measured resonant and metastable states coincide within the experimental errors. It was observed that values from measurements of both methods are in good agreement.
Photoluminescence Study of ZnSe Single Crystals Obtained by Solid Phase Recrystallization under Different Pressure Conditions. Effects of Thermal Tre…
2002
ZnSe single crystals, obtained by the Solid Phase Recrystallization (SPR) method under three different pressure conditions, 10 and 5 atm of Se, and 2 atm of argon, have been investigated by means of photoluminescence (PL) and optical microscopy. Special attention has been paid to the surface state of the samples. Samples recrystallized under 10 atm of Se present the best rate between the PL response for the excitonic zone and the deep level one that shows a clean PL emission without significant peaks and/or bands. The presence of slip bands has been detected and analysed by means of optical microscopy and photoluminescence. In order to study the changes introduced by post growth thermal tre…
Rotation of methyl radicals in a solid krypton matrix
2009
Electron spin resonance (ESR) measurements were carried out to study the rotation of methyl radicals (CH(3)) in a solid krypton matrix at 17-31 K temperature range. The radicals were produced by dissociating methane by plasma bursts generated by a focused 193 nm excimer laser radiation during the krypton gas condensation on the substrate. The ESR spectrum exhibits only isotropic features at the temperature range examined, and the intensity ratio between the symmetric (A) and antisymmetric (E) spin state lines exhibits weaker temperature dependence than in a solid argon matrix. However, the general appearance of the methyl radical spectrum depends strongly on temperature due to the pronounce…
A theory ofnonverticaltriplet energy transfer in terms of accurate potential energy surfaces: The transfer reaction from π,π* triplet donors to 1,3,5…
2004
Triplet energy transfer (TET) from aromatic donors to 1,3,5,7-cyclooctatetraene (COT) is an extreme case of "nonvertical" behavior, where the transfer rate for low-energy donors is considerably faster than that predicted for a thermally activated (Arrhenius) process. To explain the anomalous TET of COT and other molecules, a new theoretical model based on transition state theory for nonadiabatic processes is proposed here, which makes use of the adiabatic potential energy surfaces (PES) of reactants and products, as computed from high-level quantum mechanical methods, and a nonadiabatic transfer rate constant. It is shown that the rate of transfer depends on a geometrical distortion paramet…
Dynamics of spin state conversion processes in the solid state
1989
High spin (HS) ⇌ low spin (LS) conversions in transition metal complexes are nonradiative transitions between spin states. In this contribution, we present a study of the temperature and pressure dependence of the HS ⇌ LS intersystem crossing dynamics. For some iron(II) spin-crossover complexes, the rate constants were determined by line shape analysis of57Fe Mossbauer spectra. Their temperature dependence is described by an Arrhenius equation, their pressure dependence is interpreted within absolute rate theory. HS → LS conversion rates at low temperatures were determined from the relaxation of light-induced formation of HS states, monitored by optical spectroscopy. Deviations from a simpl…
Determinants and efficiency of Pakistan's chemical products' exports: An application of stochastic frontier gravity model.
2019
The estimation of efficiency of industry-specific exports is very important to find exports' gap and to frame exports promotion policy for targeted industry. This study attempts to investigate the main determinants of chemical products' exports of Pakistan with 62 trading partners by applying Stochastic Frontier Analysis (SFA) on an augmented gravity model for a period 1995-2015. The results corroborate that chemical products' exports follow gravity patterns. This study finds a negative and significant impact of import tariff on exports of chemical products while the positive impact of devaluation has been observed. Further, the estimations also take into account the impact of Preferential …
Dressed emitters as impurities
2021
Dressed states forming when quantum emitters or atoms couple to a photonic bath underpin a number of phenomena and applications, in particular dispersive effective interactions occurring within photonic bandgaps. Here, we present a compact formulation of the resolvent-based theory for calculating atom-photon dressed states built on the idea that the atom behaves as an effective impurity. This establishes an explicit connection with the standard impurity problem in condensed matter. Moreover, it allows us to formulate and settle in a model-independent context a number of properties previously known only for specific models or not entirely formalized. The framework is next extended to the cas…
Full configuration interaction calculation of singlet excited states of Be3
2004
The full configuration interaction (FCI) study of the singlets vertical spectrum of the neutral beryllium trimer has been performed using atomic natural orbitals [3s2p1d] basis set. The FCI triangular equilibrium structure of the ground state has been used to calculate the FCI vertical excitation energies up to 4.8 eV. The FCI vertical ionization potential for the same geometry and basis set amounts to 7.6292 eV. The FCI dipole and quadrupole transition moments from the ground state are reported as well. The FCI electric quadrupole moment of the X (3)A(1) (') ground state has been also calculated with the same basis set (Theta(zz)=-2.6461 a.u., Theta(xx)=Theta(yy)=-1/2Theta(zz)). Twelve of …
Obesity and Outcomes in COVID-19: When an Epidemic and Pandemic Collide.
2020
Obesity has reached epidemic proportions in the United States and in much of the westernized world, contributing to considerable morbidity. Several of these obesity-related morbidities are associated with greater risk for death with coronavirus disease 2019 (COVID-19). Severe acute respiratory syndrome coronavirus 2 penetrates human cells through direct binding with angiotensin-converting enzyme 2 receptors on the cell surface. Angiotensin-converting enzyme 2 expression in adipose tissue is higher than that in lung tissue, which means that adipose tissue may be vulnerable to COVID-19 infection. Obese patients also have worse outcomes with COVID-19 infection, including respiratory failure, n…
The Southern African Development Community (SADC): An Analytical Overview of Its History, Policies and Institutional Framework
2017
This chapter gives fundamental background information about the history and development of regionalism in Southern Africa and about the current state of the SADC as a modern regional integration organisation. In terms of an analytical overview, Muntschick reflects briefly on the formation, character and objectives of the region’s old regionalisms such as the Southern African Customs Union (SACU), the Frontline States (FLS) and particularly the Southern African Development Co-ordination Conference (SADCC) as predecessors of the SADC. Also, this chapter turns to the new regionalism and provides detailed information on the SADC as an organisation, its member states, key agenda and central poli…