Renu Bala

Exchange and correlation effects on density excitation spectra of metallic quantum wires at finite temperature

We have studied the effect of exchange and correlations on the density excitation spectra of metallic quantum wires at finite temperature. The correlations are treated by incorporating the first-order self and exchange contributions into the random-phase approximation (RPA). Numerical results are presented for the spectra of the density response function and the plasmon dispersion for the gold wire on Si(557) substrate-a system studied recently by Nagao et al. (2006 Phys. Rev. Lett. 97 116802) for plasmons using electron energy loss spectroscopy. Our results for plasmons are found to agree with the experimental data. Though the first-order correction is small at currently accessible wire parameters, it becomes significant with increasing coupling parameter r(s). The effect of temperature on plasmons is found to be small for the wire system investigated experimentally. However, temperature has a significant effect on the spectra of the response function. We have also calculated the static structure factor, the pair-correlation function and the correlation energy at zero temperature in the first-order theory to check its applicability in dealing with correlations. Results are compared directly with the available Monte Carlo simulation data. It is found that the static correlation functions improve significantly over the RPA with the increase of r(s). On the other hand, the correlation energy shows very good agreement for r(s) ≤ 5 and wire widths b ≥ a(0). For smaller b, the agreement is good up to relatively smaller r(s).

DCTA Titration of iron(III) with p-aminosalicylic acid and sodium azide as indicators.

Iron(III) has been determined by DCTA titration with p-aminosalicylic acid and sodium azide as indicator at pH 1.4-3.5. The titrations are rapid, simple, accurate and reversible and as little as 0.15 mg of iron(III) can be determined in the presence of up to 100 times as much of certain ions. Cadmium, zinc, lead, copper(II), aluminium, thorium, oxalate, phosphate, fluoride and sulphide interfere. The method is utilized for determination of iron(III) in presence of copper(II) or lead and in limestone, cement and haemetite.

Effect of Exchange‐correlations and Temperature on Plasmons in Nano‐scale Gold Wire

Seeking a theoretical explication of plasmons observed recently in gold wire by Nagao et al. [Phys. Rev. Lett. 97, 116802 (2006)], we have investigated the role of exchange‐correlations and finite temperature. The Green’s function approach is used to incorporate the first‐order exchange and self‐energy corrections to the random‐phase approximation. Inclusion of correlations is found to introduce a red shift in plasmon energy, and the calculated dispersion shows a very good agreement with the experiment. In contrast, temperature does not have a significant effect on plasmons under experimental conditions, i.e., for temperatures as high as the room temperature.

Polarographic study of the complexes of cadmium(II) and lead(II) with methoxyacetate ions

Reduction of the complexes of cadmium(II) and lead(II) atdme in aqueous and aqueous-methanol media at μ = 1.0 M(NaClO4) at 15 ±0.1 and 25 ±0.1°C is reversible and diffusion-controlled. Four complex species are formed in either case. The overall stability constants of 1:1,1:2, 1:3 and 1:4 complexes have been determined. Lead(II) complexes are much stronger than the corresponding cadmium(II) complexes.

Internal magnetic hyperfine fields at Hf nuclei in iron, cobalt and nickel hosts

AbstractIntegral perturbed angular correlation technique has been used to measure the internal hyperfine magnetic fields at Hf nuclei in Fe, Co and Ni matrices. These represent a consistent set of measurements with diffused sources. The 9+/2 (208 keV) 9−/2 (113 keV) 7−/2 cascade in the decay of177Lu→177Hf was used for measurements. The results obtained are:

Spin polarized electrons in a metallic quantum wire

\begin{gathered} H_{Fe}^{Hf} = - 266 \pm 47 kG, \hfill \\ H_{Co}^{Hf} = - 116 \pm 18 kG, \hfill \\ H_{Ni}^{Hf} = - 118 \pm 26 kG. \hfill \\ \end{gathered}

Erratum to: Particle density and transition temperature of weakly interacting quantum gases

These measurements are compared with previous results and discussed in terms of methods of source preparation.