We report room temperature angle-resolved photoemission experiments on 1T-TaS 2 and 1T-TaSe 2 complemented by density-functional theory calculations. Fermi-surface mapping experiments in the charge-density wave ͑CDW͒ phase are similar for the two compounds and do not show symmetries due to the CDW-induced new Brillouin zones. However, the band structure a few eV below the Fermi level (E F) displays a clear modulation that we relate, in both cases, to the CDW. At E F , the spectral weight distribution reflects the band structure of the normal state, but no clear quasiparticle crossing is located. Near the zone center ⌫ , CDW-split quasilocalized Ta dz 2 subbands are observed in the vicinity of E F. For 1T-TaS 2 and 1T-TaSe 2 , they are thermally populated slightly above E F and close to E F , respectively. The observed behavior can be understood in terms of the CDW reconstructed, spectral function weighted band structure.

The transition from OLD SPACE to NEW SPACE along with increasing commercialization has a major impact on space flight, in general, and on electric propulsion (EP) by ion thrusters, in particular. Ion thrusters are nowadays used as primary propulsion systems in space. This article describes how these changes related to NEW SPACE affect various aspects that are important for the development of EP systems. Starting with a historical overview of the development of space flight and of the technology of EP systems, a number of important missions with EP and the underlying technologies are presented. The focus of our discussion is the technology of the radio frequency ion thruster as a prominent member of the gridded ion engine family. Based on this discussion, we give an overview of important research topics such as the search for alternative propellants, the development of reliable neutralizer concepts based on novel insert materials, as well as promising neutralizer-free propulsion concepts. In addition, aspects of thruster modeling and requirements for test facilities are discussed. Furthermore, we address aspects of space electronics with regard to the development of highly efficient electronic components as well as aspects of electromagnetic compatibility and radiation hardness. This article concludes with a presentation of the interaction of EP systems with the spacecraft.

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The research into new materials with good thermoelectric properties has revealed new compounds consisting of metallic elements (Bando Y,

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