A comparative account is given of the 4.2 K linearly polarised absorption spectra of Sr,(PO,), C1 and Ca,PO,Cl crystals containing Mn0,3-, with emphasis on the differing site-group perturbations. With the inclusion of a previously undetected shoulder at 1 1 500 cm-' in the Ca,PO,Cl case, it is possible to account for the energies and polarisations of all the bands using similar values of A and B (respectively 1 1 000-1 1 500 and 500-550 cm-') but different parameters describing the tetragonal and trigonal site perturbations. It is confirmed that all bands in the visible are of ligand-field type and that the lowest charge-transfer band is at 32000-33000 cm-I.

We report the results of the development and realization of a program using LabVIEW software to simulate the technique utilized in the laboratory to construct a phase diagram that represents a liquid–vapor equilibrium. The program has been set up so that the student can work as if in a real laboratory, including mistakes usually made in this kind of measurement.

No abstract

The polarized electronic spectrum of MnO2-doped in crystals of Ca2PO4C1 has been measured at 4.2 K from 5000 to 40 000 cm-'. From a careful examination of the possible excited states and of the lattice site-group perturbation, the four observed bands in the region 8000-24000cm-' are assigned as ligand field bands and the other two more intense beyond 24 000 cm-' are assigned as charge transfer. The assignments are supported by the observed polarizations and by ligand field calculations which give a good fit to the energies and the relative intensities.

No abstract