Preliminary study of the thermally stimulated blue luminescence of ulexite

In this paper, novel results on the blue thermally stimulated luminescence (TSL) emission of ulexite (NaCaB₅O₆(OH)₆·5H₂O) have been studied. The four maxima appearing at 60, 110, 200 and 240°C on the TSL glow curves of this borate could be respectively associated to: (i) the first dehydration (NaCaB₅O₆(OH)₆·5H₂O→NaCaB₅O₆(OH)₆·3H₂O), (ii) the creation-annihilation of the three-hydrated phase, (iii) the Na-coordinated chains dehydroxylation and the starting point of the alkali self-diffusion through the lattice and (iv) the amorphisation of the lattice. These results are fairly well correlated with the differential thermal analyses (DTA), in situ thermal observations under environmental scanning electron microscope (TESEM) and thermal X-ray diffraction (TXRD) techniques.     

Rovibrational dynamics of the RbCs molecule in static electric fields. Classical study

We study the classical dynamics of the RbCs molecule in the presence of a static electric field. Under the Born–Oppenheimer approximation, we perform a rovibrational investigation which includes the interaction of the field with the molecular polarizability. The stability of the equilibrium points and the phase space structure of the system are explored in detail. We find that, for strong electric fields or for energies close to the dissociation threshold, the molecular polarizability causes relevant effects on the system dynamics.     

Synthesis,characterization and thermal behaviour of 2,6- and 3,4-dimethylpyridinium and 2,4,6-trimethylpyridinium octamolybdates

2,6- and 3,4-dimethylpyridinium and 2,4,6-trimethylpyridinium octamolybdates were synthesized and characterized and their thermal decompositions were studied by means of thermogravimetry. The thermal stabilities follow the sequence: 2,4,6-TMPO <2,6-DMPO <3,4-DMPO, which seems to be related to the positions of the methyl groups on the pyridine ring. Kinetic parameters were calculated for the first decomposition step of the two dimethylpyridinium octamolybdates. A nucleation mechanism is proposed. The best fit corresponds to a random nucleation (one nucleus per particle) controlled equation. The calculated activation energies were 120.9 and 133.7 kJ/mol^?1 for the 2,6- and the 3,4 derivative, respectively.