Search results for " transition"

Investigations of the Microstructure of Lipid Interface Films

1990

The phase behaviour of phospholipid monolayers at electrolyte/gas interfaces is studied by fluorescence microscopy. At the LE/LC phase transition, phase separation leads to a Wigner-type lattice structure. The observations are quantified using digital image processing. The results show that the phase transition comprises three different regimes.

Low-lying Rydberg states of HCl.

2008

Vertical excitation energies belonging to some different Rydberg series of hydrogen chloride have been determined with a coupled-cluster theoretical approach. These excitation energies have allowed us to calculate electric dipole transition intensities in HCl and allow additional assessment of the calculation approach presently used to provide an adequate description of the valence and Rydberg states of HCl. The molecular quantum defect orbital has been applied to the calculation of oscillator strengths. In particular, new insight is given on the assignment of states as the R1Pi, the 1Delta(4dpi and 5ppi), the 1Sigma+(4dpi), and the nddelta(1Pi, 1Phi) and 4f states.

Temperature dependence of the static structure factor of ortho-terphenyl in the supercooled liquid regime close to the glass transition

1993

Abstract Studying the temperature dependence of the static structure factor of ortho-terphenyl from the liquid state down to the glass we find that the main peak of S ( Q ) is split into two maxima which behave quite differently. While the maximum at Q =1.4 A −1 is not much affected by the temperature variation the one at 1.9 A −1 is significantly enhanced. This effect is connected with a change of the short range order, i.e. of the intermolecular distances, but evolves continuously. Thus the dynamic anomalies that have been observed in this system around a characteristic temperature T c ≈290 K are not simply due to a discontinuous change in S ( Q ) but can be attributed to the existence of…

Electronic Spectra of 2,2‘-Bithiophene and 2,2‘:5‘,2‘ ‘-Terthiophene Radical Cations:  A Theoretical Analysis

2001

Analysis of the electronic spectra of 2,2‘-bithiophene and 2,2‘:5‘,2‘ ‘-terthiophene radical cations has been performed by using multiconfigurational second-order perturbation theory (CASPT2). Atomic natural orbital (ANO) type basis sets of split valence quality, including polarization functions on all heavy atoms, have been used. In agreement with experimental data, in the energy range below the lowest optically allowed transition of the respective neutral system, theoretical results predict two main absorption bands for both cations. The 22Au and 32Au states computed at 1.94 and 2.80 eV, respectively, are related to the corresponding band maxima recorded for bithiophene cation. The 12B1 s…

Size-Dependent Spin Switching in Robust Fe-triazole@SiO2 Spin-Crossover Nanoparticles with Ultrathin Shell

2019

<p>A familly of chemically robust hybrid [Fe(Htrz)2(trz)](BF4)@SiO2nanoparticles (NPs) presenting different sizes (from ca. 90 to 28 nm) and an ultrathin silica shell (< 3 nm) have been prepared. All NPs present a characteristic abrupt spin transition with a subsequent decrease in the width of the thermal hysteresis upon reducing the NP size.<br></p>

Spin Transition Molecular Materials: New Sensors

2002

This short review article concerns a new family of iron(II) spin transition chain compounds containing 4-R-1,2,4-triazole derivatives whose properties have been followed by several physical techniques. A clear evidence of the LIESST effect at 20 K has been found for one of these materials by 57Fe Mossbauer spectroscopy. Potential applications in terms of pressure and thermal sensors are discussed.

1992

Inelastic Neutron Scattering Experiments on Van der Waals Glasses - A Test of Recent Microscopic Theories of the Glass Transition

1989

Etude realisee sur un verre d'o-terphenyle afin de montrer l'existence d'une relaxation secondaire presentant des caracteristiques inhabituelles et le comportement Kohbrausch de la fonction de correlation de densite decrivant la relaxation structurale

Structure and phase transition in (C2H5NH3)3Sb2Cl 9•(C2H5NH3)SbCl4; x-ray, DSC and dielectric studies

2000

Abstract The structure of (C2H5NH3)3Sb2Cl9 • (C2H5NH3)SbCl4 at 295 K has been determined. The crystals are orthorhombic, space group Pna21 (a -16.925(3), b = 24.703(5), c = 7.956(2) Å, V = 3326.4(12) Å3 , Z = 4, dc= 2.018, dm= 2.01(1) Mg m-3). They consist of an anionic sublattice composed of two different polymeric zig-zag chains. One is built of Sb2Cl9 3- units (corner sharing octahedra) and the other one is made of corner sharing SbCl5 2-square pyramids. In the cavites between the polyanionic chains four non-equivalent ethylammonium cations are located. Three of them are disordered. The cations are connected to the anions by weak N-H...Cl hydrogen bonds. A first order phase transition of…

Phase transitions and distortion of [BiCl6]3– octahedra in (C3H5NH3)3[BiCl6] – DSC and single-crystal X-Ray diffraction studies

2004

The DSC diagram of tris(allylammonium) hexachlorobismuthate(III), (C3H5NH3)3[BiCl6], revealed three anomalies at 152, 191 and 299 K. The structure of the salt was determined at 200 and 315 K, below and above the high-temperature phase transition at 299 K. In both phases the crystals are monoclinic. At 200 K the space group is C2/c whereas at 315 K it is C2/m. The structures, at both temperatures, are composed of [BiCl6]3− octahedra and allylammonium cations. The organic and inorganic moieties are attracted to each other by a network of the N-H. . .Cl hydrogen bonds. The relationship between corresponding parameters of the unit cells has been found. The phase transition at 299 K, of the orde…