Background and line interference corrections in quantitative GD-OES – New approaches to an old problem

The origin of radiative background in GD-OES is discussed, in connection with the problem of multi-matrix measurements in depth profile analysis. Backed by some experimental evidence in the form of line scans, it is argued that line emission from sample material and the plasma gas (Ar) make up the dominating contributions to the radiative background. The contribution from Ar, in this work termed Matrix-independent Background (MIB), is investigated in more detail. It is shown that, at constant voltage and current, the Ar emission intensity is nearly constant and independent of the pressure, but somewhat matrix-dependent. It is suggested that the MIB can be expressed as a linear function of the intensity of an Ar reference line. This idea is tested experimentally by making intensity measurements on a large set of calibration standards of varying composition. The results are fitted to a calibration function which allows optional definitions of the MIB. It is shown that with a MIB defined as a linear function of the Ar intensity, the different contributions to the spectral background can be more accurately determined than with the MIB defined as a constant.     

Random Copolymers of 1,5-Dioxepan-2-one

ABSTRACT

Copolymers of 1,5-dioxepan-2-one (DXO) and e-caprolactone (?-CL), δ-valerolactone (δ-VL) or L-lactide (LLA) have been synthesized and characterized. High molecular weight copolymers were obtained using stannous-2-ethyl hexanoate as catalyst in bulk. Reactivity ratios for the copolymerization of DXO and δ-VL were determined at 110°C as r_VL=0.5 and r_DXO=2.3. At high conversion, depolymerization of δ-VL occurred, resulting in lower molecular weight and variations in the copolymer composition.

Physical properties, such as crystallinity and melting temperature of the DXO-copolymers proved to be strongly dependent on the choice of comonomer and on the molar composition of the copolymers. DXO appears to be incorporated into the poly-?-caprolactone (PCL) crystals and to some extent into the poly-δ-valerolactone (PVL) crystals, resulting in a more gradual decrease in crystallinity with increasing amount of DXO.     

Using Operational Analysis in Simulation: A Queueing Network Example

The calculation of certain performance measures in queueing network simulation using operational analysis is presented. A systematic approach to the gathering of output and calculation of performance measures for quantitative system-performance analysis is demonstrated. The assumptions used in operational analysis to derive performance-measure relationships are verifiable by examining the output generated by the simulation. Any errors in assumptions revealed by the output may be measured, and these error measures used to determine correction terms. The performance-measure relations may still be used, even when the assumptions upon which they are based are in error, by adding these correction terms to the performance-measure values obtained. The results will be exact values for the performance measures over the period of the simulation. Calculations of performance measures, error measures and correction terms are illustrated with an example queueing network simulation.     

Experimental transition probabilities and Stark broadening for singly-ionized bismuth

Absolute strengths and Stark broadening parameters of the prominent (4200–6900 Å) lines of Bi(II) have been measured in emission using a gas-driven shock tube. Thermodynamic and photometric variables were determined redundantly. Comparison of the experimental ? values (accuracies of 27–50%) with literature data on the homologous structure sequence N(II), P(II) discloses systematic behavior similar to trends reported for the C(II), Si(II), Ge(II), Sn(II), and Pb(II) sequence. Parameters for Stark-effect broadening (accuracies of 25–30%) are compared with predictions of a semi-empirical model.     

Quantum nonlocality in the excitation energy transfer in the Fenna–Matthews–Olson complex

The Fenna–Matthews–Olson (FMO) complex—a pigment protein complex involved in photosynthesis in green sulfur bacteria—is remarkably efficient in transferring excitation energy from light harvesting antenna molecules to a reaction center. Recent experimental and theoretical studies suggest that quantum coherence and entanglement may play a role in this excitation energy transfer (EET). We examine whether bipartite quantum nonlocality, a property that expresses a stronger‐than‐entanglement form of correlation, exists between different pairs of chromophores in the FMO complex when modeling the EET by the hierarchically coupled equations of motion method. We compare the results for nonlocality with the amount of bipartite entanglement in the system. In particular, we analyze in what way these correlation properties are affected by different initial conditions. It is found that bipartite nonlocality only exists when the initial conditions are chosen in an unphysiological manner and probably is absent when considering the EET in the FMO complex in its natural habitat. It is also seen that nonlocality and entanglement behave quite differently in this system. In particular, for localized initial states, nonlocality only exists on a very short time scale and then drops to zero in an abrupt manner. As already known from previous studies, quantum entanglement between chromophore pairs, on the other hand, is oscillating and exponentially decaying and follow thereby a pattern more similar to the chromophore population dynamics. The abrupt disappearance of nonlocality in the presence of nonvanishing entanglement is a phenomenon we call nonlocality sudden death; a striking manifestation of the difference between these two types of correlations in quantum systems.     

Fusion around the barrier for 7Li+12C

Fusion cross-sections for the ⁷Li + ¹²C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections due to the breakup of ⁷Li may not be significant for ⁷Li + ¹²C reaction at energies around the barrier.     

Secondary ion yields produced by keV atomic and polyatomic ion impacts on a self-assembled monolayer surface

A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd.     

Collinear laser-ion beam determination of hfs in Cs II

By making use of the “velocity bunching” effect in collinear laser-ion beam spectroscopy, the hfs of the $\text{5}\text{p}{}^5{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{5}\text{d}\text{[}\text{3}\text{2}\text{]}{}^0{}_2\text{→}{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{6}\text{p}\text{[}\text{3}\text{2}\text{]}{}_2$ transition in Cs II has been determined. A 30% reduction in linewidth compared with measurements using perpendicular laser-ion beam geometry is observed. The results for the $\text{6}\text{p}\text{[}\text{3}\text{2}\text{]}{}_2$ level are compared with semi-empirical calculations.     

A contribution to the solution of the problem of quantification in surface analysis work using glow discharge atomic emission spectroscopy

The emission intensity from spectral lines has been studied in a Grimm-type glow discharge lamp (GDL). The variation in intensity of Ar I lines was investigated in order to exclude the influence of the sample sputtering rate. The variations in intensity of several analytical lines were then studied and compared with the sample sputtering rate. It was concluded that the sample atom number density in the plasma saturates with increasing voltage. An empirical intensity expression, taking into account the current, voltage and sample composition is presented. This expression was used for the determination of elemental concentrations in Cu based alloys, using a single steel reference sample as standard. An application of this procedure to a surface analysis problem is presented, and the results are compared with atomic absorption measurements. Good agreement was obtained, indicating that surface analysis data can be quantified in a simple and straightforward manner.