Non-metal compounds

Concerning non-metallic compounds, the antiknocking properties of nitrogen compounds such that derivatives of aniline, indole and quinoline, and certain phenol derivatives have been mentioned. 

J0rgensen, C. K., Berthou, H. Photo-electron Spectra Induced by X-rays of Above 600 Non-metallic Compounds Containing 77 Elements, Mat. fys. Medd. Dan. Vid. Selskab (Copenhagen) 38, no. 15 (1972)... 

OPTICAL STUDIES OF NON-METALLIC COMPOUNDS UNDER PRESSURE... 

Ever since the foundations of spectroscopy were laid the problem of the relationship between the optical spectra emitted or absorbed by matter and the microscopic properties of the matter has been regarded as a fundamental problem. A class of very interesting systems with this regard is provided by non-metallic compounds of rare-earth ions with partially filled 4f shells. Their rich electronic structure is only weakly perturbed by the environment and provides a detailed fingerprint of the surrounding arrangement of atoms and their interactions with the f-electrons. 

The aim of this chapter is to present a review of the high pressure optical studies on rare-earth ions in non-metallic compounds. Other methods, as for example neutron scattering, magnetic resonance techniques or MoBbauer spectroscopy will not be considered here, unless they provide additional valuable information to the optical studies. It will be demonstrated that the problem of host lattice structural dependence of 4f/v states can be effectively tackled by high pressure techniques and hopefully the interest for further, more refined high pressure studies of this problem can be stimulated. 

Before continuing, some words must be said with regard to the terms rare earths and f elements used in this chapter. The term rare earths includes the elements Sc, Y and the lanthanides La through Lu. However, this chapter solely deals with divalent or trivalent rare-earth ions which are optically active, i.e., possess a partially filled f-shell. Thus, although the term rare earths is used in this chapter, it should be kept in mind that the elements Sc, Y, La, and Lu are excluded. In some exceptional cases the more general term f elements will be used, as for example when high pressure studies on actinide ions with a partially filled 5f shell are discussed. There are only few studies on 5f elements in non-metallic compounds under pressure, however, it seems interesting to compare the results found for these ions with those for the 4f-elements. 

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