ESR and Optical Studies on γ-Irradiated MgCl₂ Single Crystals

Discovering Hidden Material Properties of MgCl2 at Atomic Resolution with Structured Temporal Electron Illumination of Picosecond Time Resolution

“…At low dose rates (blue curve), the bandgap E g of α‐MgCl 2 and plasmon excitations are the dominant features in the spectra. In contrast, at high dose rates (red curve), defect levels dominate because chlorine atoms are removed from their lattice sites and vacancies are formed . Thus, our EELS spectra capture the generation of chlorine vacancies, which shows that chlorine losses are accelerated by increasing dose rates.…”

Genesis of MgCl2‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

“…However, the final pattern is the same as that obtained from MgCl 2 -6MeOH. [87] This phenomenon is more pronounced for the MgCl 2 -EtOH -250 sample (Figure 3b). [59] DR UV-Vis-NIR spectroscopy was applied to monitor the evolution of the electronic properties during the transition from the MgCl 2 -6MeOH and MgCl 2 -6EtOH precursors to the activated MgCl 2 (Figure 3).…”

“…[86] A second envelope of bands is detectable in the final spectrum (spectrum 7) at 33000 and 23500 cm À1 , which are responsible for the goldenrod yellow color of the samples and are compatible with the presence of trapped electrons, i. e. color centers. [87] This phenomenon is more pronounced for the MgCl 2 -EtOH -250 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 sample (Figure 3b). These bands are not affected by the successive adsorption of molecules (including H 2 O), suggesting that the color centers are buried in the bulk of the MgCl 2 (and hence not relevant to the catalysis).…”

Characterization of a model Ziegler–Natta catalyst for ethylene polymerization

“…It is known, that upon irradiation of alkali and alkali-earth halogenides with x-ray and gamma-radiation or electrons color centers ͑F-centers͒ with unpaired electrons are formed. [30][31][32] If these centers are created in large amounts, they can be stabilized by the formation of metal clusters. Such metal clusters show conduction electron-spin resonance ͑CESR͒.…”

“…While color centers show a Curietype temperature behavior (ϳ1/T), CESR signals are rather weak and do not exhibit a pronounced temperature dependence in the range of temperatures used here, as the susceptibility is equal to the temperature-independent Pauli- susceptibility. [30][31][32][33] Furthermore, the linewidths of these clusters are very large as long as quantum size effects are not important. Let us first consider the nonepitaxial film.…”