Characteristic behaviour of plasma fluctuations inside a plasma bubble in presence of a magnetic field due to the formation of a potential well

Experiments were carried out to observe the effect of a magnetic field and grid biasing voltage in presence of a plasma bubble in a magnetized, filamentary discharge plasma system. A spherical mesh grid of 80% optical transparency was negatively biased and introduced into the plasma for creating a plasma bubble. Diagnostics via an electrical Langmuir probe and a hot emissive probe were extensively used for scanning the plasma bubble. Plasma floating potential fluctuations were measured at three different positions of the plasma bubble. The instability in the pattern showed the dynamic transition from periodic to chaotic for increasing magnetic fields. Time scale analysis using continuous wavelet transform was carried out to identify the presence of non‐linearity from the contour plots. The mechanisms of the low‐frequency instabilities along with the transition to chaos could be qualitatively explained. Non‐linear techniques such as fast Fourier transform, phase space plot, and recurrence plot were used to explore the dynamics of the system appearing during plasma fluctuations. In order to demonstrate the observed chaotic phenomena in this study, characteristics of chaos such as the Lyapunov exponent were obtained from experimental time series data. The experimentally observed potential structure is confirmed with numerical analysis based on fluid hydrodynamics.     

On the Debye‐Waller factor and Debye temperature of CdO nanoparticles

Theoretical calculation on the phonon dispersion of CdO nanoparticles at room temperature is reported here for the first time. The mean square amplitude, Debye–Waller factor and Debye temperature are calculated for CdO nanoparticles from the phonon spectrum and compared with the experimental results obtained from Rietveld refinement of XRD pattern of the CdO nanoparticles. The thermal stability of the nanoparticles is studied from both the experimental and theoretical calculations of melting point which is found to be 3686 K and 3951 K, respectively, greater than that of bulk CdO. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Experimental observation of intermittent route to chaos in magnetized filamentary discharge plasma due to the cylindrical plasma bubble

We delineate an experimental observation of the effect of the magnetic field along with mesh grid biasing in the presence of a cylindrical plasma bubble in a filamentary discharge magnetised plasma system. The cylindrical mesh grid of 80% optical transparency has been negatively biased and introduced in the plasma for creating a plasma bubble. Plasma floating potential fluctuations have been taken outside (LP1) and inside (LP2) of the plasma bubble. It has been noticed that as the external magnetic field is increased the oscillation pattern shows intermittent route to chaos as the system evolved from regular type of relaxation oscillations (of larger amplitude) to an irregular type of oscillations (of smaller amplitude) We have used recurrence quantification analysis (RQA) to the observed intermittency to chaos in the plasma. The main measures of RQA are laminarity (LAM) and determinism (DET). The laminarity measure can be associated with the average time between the chaotic burst in the intermittency. It has also been observed that the DET depends on the control parameter and decreases exponentially, features like a dip in skewness and a hump in the kurtosis with the variation of control parameter have been noticed, which are the strong evidence of intermittent behaviour of the system. Further, a numerical model has been developed to the observed experimental analysis of the intermittent route to chaos.     

Thiazole-tethered biaryls as fluorescent chemosensors for the selective detection of Fe3+ ions

3-Amino-5-(thiazol-2-yl)-[1,1′-biaryl]-2,4-dicarbonitriles have been synthesized employing a facile one-pot pseudo four-component domino strategy. All these thiazole-tethered biaryls exhibited blue fluorescence under UV lamp. Based on the high relative quantum yield, three compounds namely, 4a , 4d , and 4i , were chosen to explore the metal interference studies. Against several metal ions, these three thiazole-tethered biphenyl probes were found to be effective fluorescent chemosensors for the selective and sensitive detection of Fe³⁺ ions with a lower detection limit of 0.18, 0.12, and 0.16 μM, respectively.