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  • The final test that was performed was

    2021-03-29

    The final test that was performed was to determine whether the trigger points of the current limiters are stable across a wide temperature range. This test was performed within a thermal-vacuum chamber on each current limiter individually. All the current limiter trip currents were set to approximately 2.5A. We can see from the results in Fig. 27 that the trigger current remained fairly constant, a total variation of 3.0%, 6.5% and 8.5% for the Power Distribution Current Limiter, Autonomous Current Limiter and Controlled Current Limiter, respectively, across a temperature range of–25 to 85°C. The specific variation can be attributed to the characteristics of the components used – for example, the variations of the resistance with regards to temperature, as well the variations of the triggering point (of the internal comparator) of the FET drivers.
    Conclusion
    Introduction Lanthanide (Ln) elements, which have progressively filled 4f electrons, are important in various applications, such as optical and magnetic materials. Particularly, the large magnetic moment and its anisotropy have attracted much attention because of its potential property of single-molecule magnets [1], [2], [3]. In smad pathway to transition metal complexes, lanthanide complexes generally show a negligible contribution of the open-shell 4f orbitals to the bonding [4]. Because the 4f orbitals are localized in the inner-shell, and the possible interactions with ligands are effectively shielded by the outer 5s and 5p closed-shell electrons, they remain as open-shell unpaired orbitals and are weakly perturbed by the ligands. The combination of the spin-orbit coupling (SOC) and weak ligand field effect makes the electronic structure of Ln complexes highly complicated. Thus, their theoretical study is one of the most challenging subjects in current quantum chemistry. Recently, we have performed an ab initio study of the metal-ligand interaction in the anion and neutral Ln(COT)2 complexes to analyze their anion photoelectron spectra (PES) [5], [6], [7]. Most of these complexes are believed to consist of a trivalent Ln3+ sandwiched with two aromatic rings of COT2− (COT=1,3,5,7-cyclooctatetraene) [7]; thus, they can be considered a 4f analogue of metallocene. The computed results show that the anion Ln(COT)2− complexes have the D8h structure, and the highest occupied molecular orbital (HOMO) essentially consists of the ligand πe2u group orbital with the irreducible representation (irrep) of e2u. As previously described, the Ln 4f orbitals are split notably weakly into fourfold levels with a2u, e1u, e2u, and e3u irreps, and even the 4fe2u orbital hardly participates in the HOMO with the identical irrep of e2u. (In the following text, the HOMO is denoted by e2u as in [5].) However, the situation drastically changes in the neutral Ln(COT)2 complexes, which have the major electronic configuration of 4fe2u3 with a hole in the HOMO. Some ligand field split components are stabilized by a specific configuration interaction with minor configurations of 4f−1e2u4 [8], [9], [10], [11], [12], [13], [14], [15], [16]. Since this minor configurations are derived by a one-electron excitation from the 4fe2u orbital to the e2u orbital, this configuration mixing represents a resonance interaction between the formal charge structures Ln3+(COT1.5−)2 and Ln4+(COT2−)2. We consider this relaxation effect as the origin of the interesting experimental results that the lowest X peak of PES is only split for the middle-range Ln complexes [7]. In the previous paper, we discussed the splitting mechanism and its Ln dependence using group theory [5]. The theoretical results based on the state-averaged complete active space self-consistent field (SA-CASSCF) and the second-order multi-configuration quasi-degenerate perturbation theory (MCQDPT2) calculations were consistent with the experimental PES [7]. The theoretically obtained splitting values were reasonably consistent with the experimental values, although the spin-orbit (SO) effect was not considered. However, following the general consensus in lanthanide chemistry, the SO effect is stronger than the ligand field effects and becomes important particularly in the late Ln series [17]. Studies on the neutral Ce(COT)2 [9], [18], [19] and entire series of the anion Ln(COT)2− complexes [20] reveal that the SO effect is not crucial in the electronic ground states, but it is expected to considerably affect the optical process and magnetic properties. Therefore, the inclusion of the SO effect can be essential to accurately describe the PES.