Physical and Chemical Properties of Wolf–Rayet Planetary Nebulae

Wolf–Rayet ([WR]) and weak-emission-line (wels) central stars of planetary nebulae (PNs) have hydrogen-deficient atmospheres, whose origins are not well understood. In the present study, we have conducted plasma diagnostics and abundance analyses of 18 Galactic PNs surrounding [WR] and wels nuclei, using collisionally excited lines (CELs) and optical recombination lines (ORLs) measured with the Wide Field Spectrograph on the Australian National University 2.3 m telescope at the Siding Spring Observatory complemented with optical archival data. Our plasma diagnostics imply that the electron densities and temperatures derived from CELs are correlated with the intrinsic nebular Hβ surface brightness and excitation class, respectively. Self-consistent plasma diagnostics of heavy-element ORLs of N2+ and O2+ suggest that a small fraction of cool (≲7000 K), dense (∼104–105 cm−3) materials may be present in some objects, though with large uncertainties. Our abundance analyses indicate that the abundance discrepancy factors (ADFs ≡ ORLs/CELs) of O2+ are correlated with the dichotomies between forbidden-line and He i temperatures. Our results likely point to the presence of a tiny fraction of cool, oxygen-rich dense clumps within diffuse warm ionized nebulae. Moreover, our elemental abundances derived from CELs are mostly consistent with asymptotic giant branch models in the range of initial masses from 1.5 to 5 M ⊙. Further studies are necessary to understand better the origins of abundance discrepancies in PNs around [WR] and wels stars.

Population Kinetics Modeling of Low-Temperature Argon Plasma

Optical emission spectroscopy has been widely used in low-temperature argon plasma diagnostics. A coronal model is usually used to analyze the measured line ratios for diagnostics with a single temperature and density. However, many plasma processing conditions deviate from single temperature and density, optically thin conditions, or even coronal plasma conditions due to cascades from high-lying states. In this paper, we present a collisional-radiative model to investigate the validity of coronal approximations over a range of plasma conditions of Te = 1–4 eV and Ne = 108–1013 cm−3. The commonly used line ratios are found to change from a coronal limit where they are independent of Ne to a collisional-radiative regime where they are not. The effects of multiple-temperature plasma, radiation trapping, wall neutralization, and quenching on the line ratios are investigated to identify the plasma conditions under which these effects are significant. This study demonstrates the importance of the completeness of atomic datasets in applying a collisional-radiative model to low-temperature plasma diagnostics.

Plasma diagnostics during deposition of Zr-B-N coatings by magnetron sputtering of UHTC ceramic in DCMS and HIPIMS modes

In this work, plasma diagnostics during the deposition of Zr-B-N coatings by DCMS and HIPIMS methods were carried out, the structural characteristics and growth rates of the obtained coatings were investigated; the regularities of the influence of the working atmosphere on the composition of the plasma, as well as on the thickness and growth rate of the coatings are revealed. It was found that the introduction of nitrogen leads to a decrease in the concentration of Zr and B ions in the plasma, as a result of which the growth rate of the coatings decreases. Note that, when using the DCMS method, predominantly argon plasma is observed, while with HIPIMS, the plasma is characterized by a large number of metal ions.