Search

The structure and the unimolecular fragmentations of the metastable dimethyl peroxide radical cation have been investigated by mass spectrometric and isotopic labeling methods as well as high‐level ab initio calculations. In line with the theoretical results, neutralization‐reionization and charge reversal experiments suggest that ionized dimethyl peroxide bears a CH3OOCH•3connectivity. In the cation the O‐O bond dissociation energy is larger than that of the neutral counterpart; in contrast, the C‐O bond strength is slightly and that of the C‐H bond significantly reduced upon ionization. These energetic changes upon one‐electron oxidation of CH3OOCH3are also reflected in the NR and CR mass spectra of CH3OOCH•+3. Further, for metastable CH3OOCH•3two major fragmentation pathways are observed: 1) Loss of a hydrogen atom by cleavage of a C‐H bond is associated with a skeletal reorganization, which gives rise to a proton‐bound formaldehyde dimer. 2) The expulsion of a CH3O•radical leads to protonated formaldehyde in a surprisingly specific double hydrogen transfer involving a [CH3OH/CH2O]•ion/dipole complex as central intermediate; this complex also accounts for other minor fragmentation channels. The structures of intermediates and transition states are calculated with the BECKE 3LYP density‐functional method employing a 6‐311++G**basis.

The article provides information on the analogue photography of Istvan Balogh, which uses the camera in a traditional analogical apparatus mode that foregoes technical interventions or alienation. It notes that Balogh's photographic style creates images through the lens and refraction of light rays. It includes varied images and large format photographs that takes every detail, every contour clearly visible to a point of technical perfection. It adds that the photographs presented left nothing that obstructs the observer's vision, yet remains mystical and retains the fictional aspect of the image.

We studied the growth of Si- and Sn-doped homoepitaxial β-Ga2O3layers on (010)-oriented substrates by metal organic vapor phase epitaxy (MOVPE). At optimal growth conditions (850°C, 5 mbar) the layers were smooth with RMS roughness values of ∼600 pm. A microstructural study by transmission electron microscopy (TEM) revealed a very high crystalline perfection of the layers. No dislocations or planar defects were observed within the field of view of TEM. Using Si as dopant, the free electron concentration could be varied in a range between 1 × 1017and 8 × 1019cm−3, while with Sn the doping range was restricted to 4 × 1017−1 × 1019cm−3. This was explained by a pronounced Sn memory effect in the MOVPE reactor that hampers achieving low carrier densities and by incorporation issues that limit the doping efficiency at high Sn doping levels. The electron mobility for a given doping density increased from ∼50 cm2/Vs for n = 8 × 1019cm−3to ∼130 cm2/Vs for n = 1 × 1017cm−3independently of the dopant. These values match the best literature data relative to β-Ga2O3bulk crystals and layers grown by molecular beam epitaxy, setting a new standard for MOVPE-grown layers.