ABSTRACT
INTRODUCTION Trihalide lanthanides are considered now to be very promising materials for new energy saving light sources — metal halide lamps. Vaporising partly under operating conditions they influence on the light emission properties. Until now the modeling of high temperature processes in such lamps to optimise the process parameters and to elongate the lifetime of metal halide lamps was founded on thermodynamic data obtained exceptionally for neutral components of vapours. However, the results of our last investigations have demonstrated that the saturated vapour over lanthanide trichlorides consists of various molecular (LnC13)„ and ionic C11.(LnC13)„ associates [1-3]. It is clear, the ions have to determine essentially electrical properties of high temperature vapour and thereby influence on the real processes taking place in the lamps. Therefore the complete thermodynamic information both on the molecular and the charged vapour constituents has to be available. The results of mass spectrometric determination of thermochemical data on LnC14 and Ln3C17 (Ln---Pr, Nd) negative ions are presented here.
