Double-hump resonance structure of the cross sections for electron impact ionization of Ar5+

Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar5+. Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute up to 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the cross sections is demonstrated and the contributions of metastable states are also taken into account.     

Double-hump resonance structure of the cross sections for electron impact ionization of Ar^5 ＋

Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar^5 ＋ .Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute upto 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the crcessections is demonstrated and the contributions of metastable states are also taken into account.     

The use of laser induced breakdown spectroscopy for the determination of Li in organic wash solutions during the preparation of lithium based oxide ceramics by sol–gel

Laser induced breakdown spectroscopy (LIBS) has been investigated for the determination of lithium in various streams generated during the preparation of lithium titanate microspheres employing internal gelation in Sol–gel. Important parameters including laser energy and acquisition delay were optimized to achieve the best signal to noise ratio during the LIBS analysis using filter paper as a solid support. The usefulness of different analytical emission lines of lithium was investigated. The developed LIBS methodology was found to be useful in developing the sol–gel process for preparing the lithium based microspheres for fusion based R&D programs.     

Application of liquid scintillation inclusion techniques for the simultaneous determination of alpha and beta activities in composite samples – A preliminary study

Present work highlights liquid scintillation inclusion techniques as a tool for simultaneous determination of gross α and β activities in composite samples. This preliminary study comprises a preamble exercise to check whether Automatic Efficiency Control (AEC) and knee point inclusion techniques which are conventionally used for analysis of two β-emitting radio-nuclides in a mixture, can be implemented for quantification of gross α and β activities in composite samples. In inclusion techniques, two counting regions are set such that there are spill-up and spill-down of pulse events in each region from both types of radio-nuclides. AEC which is built-in feature in Packard Tri-Carb 2900 TR Liquid Scintillation Counter (LSC) provides automatic counting region adjustments for single and dual label samples according to the degree of quench present in sample. While knee point inclusion technique requires manual Lower Level (LL) and Upper Level (UL) discriminator setting to define two counting regions. In the present study, α/β spiked composite samples were treated as dual label samples with α and β radio-nuclides as two distinct entities contributing to the gross activities and analyzed employing AEC and knee point inclusion techniques. Instrument discriminator settings and regions of interest (ROI) were evaluated to determine optimum counting conditions for both the techniques. Three sets of pure alpha and pure beta standards simulating the activity concentrations of real samples in terms of α/β activity ratios were used to calibrate LSC. Calibration methodology for Packard Tri-Carb 2900 TR LSC with respect to the above measurements using ²⁴¹Am, ³⁶Cl and ⁹⁰Sr/⁹⁰Y calibration standards is explained in detail. The practicability and working performance of these techniques was checked by the validation trials with spiked synthetic samples covering range of α/β activity ratios from 1:1 to 1:50 and 50:1. Procedures have been tested by comparison with, established PSA technique and repeatability has been evaluated.     

The Ising square lattice in aL×M geometry: A model for the effect of surface steps on phase transitions in adsorbed monolayers

Critical phenomena in adsorbed monolayers on surfaces are influenced by limited substrate homogeneity, such as surface steps. We consider the resulting finite-size and boundary effects in the framework of a lattice gas system with nearest neighbor attraction in aL×M geometry, with two free boundaries of lengthML, and periodic boundary conditions in the other direction (along the direction of the steps). This geometry thus models a terrace of the stepped surface, and adatoms adsorbed on neighboring terraces are assumed to be non-interacting. Also the effect of boundary fields is considered (describing the effects of missing neighbors and changed binding energy to the substrate near the boundary). Extensive Monte Carlo calculations on this model performed on a multi-transputer system are presented and analyzed in terms of phenomenological finite size scaling concepts. The fact that two scaling variables occur (/L,L/M, with being the correlation length in the bulk) is demonstrated explicitly. In the absence of boundary fields, the system forML orders nearT _c in a domain state, with domain walls running across the terrace, while at some temperature belowT _c a transition to a monodomain state occurs. This domain state slightly belowT _c is suppressed, however, by rather weak boundary fields. These results are interpreted in terms of exact theoretical predictions.