Design, fabrication and performance evaluation of a 22-channel direct reading atomic emission spectrometer using inductively coupled plasma as a source of excitation

The indigenous design, fabrication and performance evaluation of a polychromator, using inductively coupled plasma (ICP) as a source of excitation, are described. A concave holographic grating is used as the dispersing element and a Paschen-Runge mount is chosen to focus the spectra over a wide range along the Rowland circle. Twenty-two exit slits, mounted along the circle, precisely correspond to the wavelengths used for determination of up to twenty elements present in the plasma. Radiations emerging from the exit slits are detected by photomultiplier tubes placed behind them. The photomultiplier signal is recorded by an electronic system consisting of an integrator and a PC-based data acquisition system. The performance of the spectrometer has been evaluated with an ICP excitation source. Synthetic standards in deionized water containing a mixture of twenty impurities have been analysed. Typical determination limits observed for elements range from sub-ppm to ppm levels. All the elements present as impurities can be detected simultaneously. It is also observed that each element has a different emitting region in the ICP flame for which the maximum signal to the background is obtained. The determination limits obtained corresponding to these zones are the lowest. A study of the sensitive emitting zones for several elements has been carried out and the results are demonstrated by photographs of the ICP flame. The study will help in achieving the minimum value of determination limit for an impurity element

Structure and Stability of Zn, Cd, and Hg Atom Doped Golden Fullerene (Au₃₂)

Structures and properties of various complexes formed between the “golden fullerene”, Au₃₂, and group IIB atoms such as Zn, Cd, and Hg have been investigated using density functional theory (DFT). Binding energy values indicate that the group IIB atoms can form stable clusters in most of the different isomeric forms of the Au₃₂ cage. The HOMO–LUMO gap of the Au₃₂ cage remains almost the same even after doping of Zn, Cd, and Hg atoms for high symmetry clusters, while it decreases for the low symmetry isomers. The highest stable isomer for the Hg-doped Au₃₂ cluster is found to be associated with <i>I</i>_<i>h</i> symmetry with a large energy difference from the other low symmetry isomers, using generalized gradient approximation (GGA) type functionals. However, for the Zn and Cd encapsulated Au₃₂ clusters, the highest stable structures are of <i>C_s</i>[1] and <i>C</i>_5<i>v</i> symmetry, respectively, along with one low symmetry isomer for each of them, having energy very close to the respective most stable isomer. Nevertheless, depending on the energy density functional, the relative energy orderings for the various isomers are found to be modified strongly. In fact, the meta-GGA TPSS functional predicts low symmetry compact isomers to be more stable for all the metal atom doped Au₃₂ clusters. Moreover, low symmetry compact isomers are found to be more stable with the dispersion-corrected GGA type PBE functional for the Zn- and Cd-doped cluster, in agreement with the TPSS results; however, the same dispersion correction fails to reproduce the TPSS results for the Hg-doped Au₃₂ system. Structural data, energetic parameters, and spectral analysis point toward the possible experimental observation of group IIB atom doped golden fullerene, which in turn might help to understand the nature of interactions between the metal atom and the Au₃₂ cage. Furthermore, experimental investigations would likely confirm the predictive ability of the different functionals used in this work