On the difference between a point multipole and an equivalent linear arrangement of point charges in force field models for vapour–liquid equilibria; partial charge based models for 59 real fluids

The replacement of a point dipole and a point quadrupole by a corresponding linear arrangement of two point charges (+q, ?q) and accordingly three point charges (+q, ?2q, +q) is studied with respect to vapour–liquid equilibria. The dependence of saturated liquid density, vapour pressure and heat of vaporization on the choice of the distance d between the charges in the point charge arrangement is analysed. For the studied dipolar two-centre Lennard-Jones (2CLJD) and quadrupolar two-centre Lennard-Jones (2CLJQ) models, d/σ between 1/15 and 1/20 is a reasonable compromise between numerical and physical accuracy, where σ is the Lennard-Jones size parameter. The results are used to derive validated partial charge based models of 59 real fluids from previously published point dipole and point quadrupole based models.     

Magnetic circular dichroism of the first spin-forbidden transition in 2[Cr(en)3Cl3] . KCl . 6H2O

The longitudinal Zeeman effect of the ² E ←⁴ A ₂ transition of the Cr⁺³ ion in single crystals of 2[Cr(en)₃Cl₃] . KCl . 6H₂O has been measured using circularly polarized light as a function of magnetic field strength between 0 and 160 kgauss at ～80 K. The g factor for the ground state was determined to be g _‖(⁴ A ₂) = 2·01±0·05, in agreement with the E.S.R.-determined value. The ratio between the excited state g values and that of the ground state was determined; using the value g _‖(⁴ A ₂) = 1·99, the g factors g _‖(2) = 2·61±0·04 and g _‖() = 1·47±0·04 were obtained.     

Low temperature,high pressure Raman study of SbSBr

Abstract

We have measured the Raman spectra of the quasi-one-dimensional crystal SbSBr as a function of pressure at 295, 70, 37 and 25 K.

The pressure coefficients of the observed Raman modes have been determined and used to distinguish inter-from intrachain modes. Spectral features characteristic of the ferroelectric phase have been attributed to impurities or lattice imperfections and not to the presence of the ferroelectric phase, providing indication that the para-to ferroelectric phase transition occurs below 25 K.     

Low-lying levels in103Rh from Coulomb excitation

Five low-lying negative parity states of¹⁰³Rh up to 1277 keV excitation energy were observed to be Coulomb excited with 2·5–4·5 MeV protons. The de-excitation gamma rays from these levels were identified in the singles spectra recorded with a 57 cc Ge(Li) detector. The level energies, branching ratios, reduced transition probabilitiesB(E2) and the multipole mixing ratios () were obtained. The 880, 1106 and 1277 keV levels have been Coulomb excited with protons for the first time. The ambiguity in theJ values for 803 and 1106 keV levels have been resolved using ²-fits, the assigned spin values are 1/2^– and 5/2^–, respectively. The-values for 474·1 and 811·2 keV transitions were obtained for the first time. The results have been discussed in the light of previously reported results.The authors wish to thank Professor I. M. Govil for his active interest at various stages of this work. One of us (DCT) acknowledges the financial support from U.G.C., New Delhi, under Faculty Improvement Programme.     

High-spin levels in138Ce and140Nd Observed in the (α, 4n γ) reactions

Levels of¹³⁸Ce and¹⁴⁰Nd have been studied using the¹³⁸Ba(α,4nγ)¹³⁸Ce and¹⁴⁰Ce(α, 4nγ)¹⁴⁰Nd reactions. Singleγ-ray spectra,γ-γ coincidence spectra, angular and time distributions with respect to the beam bursts have been measured. A number of higher excited states with excitation energies up to about 5 MeV and with spin value up to 12 are populated in both nuclei. The lower states with spins and parities 7^?, 5^?, 6^? and 10⁺ can be explained by two-quasiparticle neutron configurations of the types (h _11/2 ^?1 ,d _3/2 ^?1 ) 7^? , (h _11/2 ^?1 ,S _1/2 ^?1 ) 5^?, 6^? and (h _11/2 ^?2 ) 10⁺. Several high-spin states observed in¹³⁸Ce and¹⁴⁰Nd can be explained qualitatively as four-quasiparticle states with two-proton-two-neutron configurations. The 3^? state at an energy of 2,137.4 keV is observed in¹³⁸Ce. The evidence for the existence of the low-lying 3^? states in¹⁴⁰Nd at 2,124.0 keV is discussed. Beside the known 9.6 ms (7^?) isomeric state in¹³⁸Ce another state at 3,538.5keV (10⁺) with a half life of about 200 ns has been observed. The observed levels in the¹³⁸Ce and¹⁴⁰Nd nuclei are compared with theoretical predictions using delta force interaction.     

Magnetic circular dichroism of theA andB bands in KI:Ga+, KI:In+, and KI:Sn2+

Magnetic circular dichroism (MCD) of theA- andB-absorption band region has been obtained at 4.2 K and 50 kG in KI:Ga⁺, KI:In⁺, and KI:Sn²⁺. The MCD spectra indicate the complex nature of these bands more clearly than the absorption spectra themselves do. TheA-band MCD consists in all cases of a positive and a negative part reflecting the structure of the absorption band. TheB-band MCD shows three peaks, two positive peaks at 4.34 and 4.41₅ eV (4.09 and 4.17₅ eV) and a negative peak at 4.38 eV (4.12₅ eV) in KI:Ga⁺ (KI:In⁺). TheB-band in KI:Sn²⁺ consists of a shoulder (b ₀) at 3.76 eV and a main band which has at least 5 sub-peaks (b ₁~b ₅) at 3.82₁, 3.84₁, 3.86₁, 3.88₀, and 3.89₅ eV; each of the subpeaks (b ₁~b ₅) gives a derivative-like MCD.The MCD shape functionf() for the transitiona _1g ² a _1g t _1u has been obtained for one set of parameter values by using the classical Franck-Condon approximation and the Monte Carlo integration method. The result can explain the observed salient features of theB- as well asA-band MCD's, indicating the validity of the Franck-Condon approximation and the interaction mode coordinates.     

Optimization of the parameters of the ideal 180° spherical analyzer

Resolution and intensity behaviour of the spherical analyzer are mainly determined by the entrance parameters (aperture angle 2α _m , relative width of the entrance slita/r ₀) and by the relative width of the exit slitb/r ₀. The mutual relation of these parameteres can be so optimized that independent of the required resolution the quantities étendue or luminosity of the spherical analyzer attain a maximum.     

Temperature dependence of the electrical resistivity of the nickel-platinum alloy system

The temperature dependence of the electrical resistivity of Ni_1?xPt_x (x = 1, 2, 3, 4, 5, 8, 10, 15, 20, 25 and 30 at.%) between 77 and 700 K has been investigated. The experimental results are interpreted according to the theoretical model developed by Mott. It is shown that for this system Matthiessen's rule is not obeyed.     

Nanoparticulate materials and regulatory policy in Europe: An analysis of stakeholder perspectives

The novel properties of nanoparticulate materials (NPM) and the rapid development of NPM based products have raised many unanswered questions and concerns by different stakeholders over its consequences for the environment and human health. These concerns have led to an increasing discussion in both the US and Europe about possible regulatory policies for NPM. In this article a comparative study of stakeholders’ perceptions on regulatory policy issues with NPM in Europe is presented. It was found that industry wants to regulate this area if the scientific evidence demonstrates that NPM are harmful, but also that the regulatory bodies do not find it necessary at this point of time to regulate until scientific evidence demonstrates that NPM are harmful. This research therefore shows that there will most likely not be any regulatory interventions until there is an established and convincing scientific knowledge base demonstrating that NPM can be hazardous. It is furthermore discussed in this article the different roles and responsibilities of the stakeholders in financing the research required to establish the necessary level of fundamental scientific evidence. It was also found that the activity of the regulatory bodies on this issue differ between the European countries.