Single crystal ESR study of copper(II)-Bis (1,1-dicyanoethylene-2,2-dithiolate)

A single crystal ESR study of [Cu(i-MNT)2] (Bu4N)2 diluted in the corresponding nickel complex is reported. Using an MO model of D4h symmetry, the bonding parameters of the first coordination sphere were calculated. The influence of the ligand spin-orbit interaction is considered. © 1973

33S and 13C hyperfine interactions in the single-crystal EPR spectra of 63Cu(II) bis(diethyl-dithiocarbamate)

A detailed analysis of the 33S and 13C ligand hyperfine interactions observed in the single-crystal EPR spectra of 63Cu-labelled copper(II)bis(diethyl-dithiocarbamate), diamagnetically diluted by the corresponding Ni(II)-complex, is reported. The 33S hyperfine tensors are nearly axial symmetric; the unique axes are found to lie along the CuS bond directions. The observation of two different sets of 33S splitting parameters is in agreement with the presence of a rhombic distortion of the planar ligand field. The 13C hyperfine tensor is isotropic within experimental error. The bonding situation of the electronic ground state is discussed. In order to explain the unusually small linewidths observed the electron spin-lattice relaxation time was measured in the temperature-range 2 ≤ T ≤ 77 K. © 1977

On the existence of a paramagnetic adduct of Ni(II)-bis-(di-n-butyl-diselenocarbamate). An EPR study

Paramagnetic adduct formation of pyridine with nickel(II)-bis(di-n-butyl-diselenocarbamate) is observed by means of EPR at 27°K. The low value of the zero field splitting and the g-factor are explained by strong spin-orbit interactions and by high covalency typical of the Se4-coordination sphere. © 1973

A single crystal EPR study of the platinum (III)-bis (maleonitriledithiolate)-monoanion

A first single crystal EPR study of a Pt3+ chelate-tetrabutylammonium-bis (maleonitriledithiolato) platinate (III)-diamagnetically diluted by the corresponding gold (III) chelate is reported. The spectra are described by a rhombic spin Hamiltonian. For some orientations of the magnetic field 33S superhyperfine splitting was observed. The 33S tensor has the maximum value perpendicular to the plane of the complex supporting a 2B3g ground state in which the half-filled out-of-plane π molecular orbital is extensively delocalized over the ligands. Furthermore, the electron spin-lattice relaxation of the Pt3+ complex was measured in the temperature range 4.2 ≤ T ≤ 16 K. Spin-lattice interactions were found to be mainly responsible for the linewidth in the Pt3+ spectra, which is larger by a factor 2 than those observed for Pd3+ and Ni3+ in the same host complex [Au(mnt)2]-. © 1977

Spin-lattice relaxation of exchange-coupled Cu2+-Cu2+ pairs and single Cu2+ ions in crystals of zinc (II) bis(diethyl-dithiocarbamate)

Detailed investigations of the spin-lattice relaxation of single Cu 2+ ions and Cu2+-Cu2+ pairs in zinc (II) bis(di- ethyl-dithiocarbamate) single crystals are reported. The measurements were made in the temperature range 1.5<T<35K at v=28.8 and 9.0 GHz using the pulse saturation and the spin-echo method, respectively. At T<5K the single-ion relaxation is defined by direct processes; at higher temperatures two-phonon Raman processes were observed. In the range 4<T<12K the data can be fitted by an Orbach-Aminov process. A calculation of the single-ion relaxation rate for the direct process has been made. Also the pair relaxation rate in the same range was calculated considering the rate equations of the populations of the triplet state. From the temperature dependence of the Orbach-Aminov process the isotropic exchange integral was derived. Low-temperature EPR measurements provided the signs of the D-tensor and of the exchange integral. From the temperature dependence of the single-ion Raman relaxation rate the Debye temperature of the host crystal was estimated. For exchange coupled pairs the anomalous frequency dependence of T1 -1 was observed

Electron spin-lattice relaxation of Cu(II) in Zn(II)-bis(diethyl-diselenocarbamate) single crystals

Using the pulse saturation method the spin-lattice relaxation rate T1 -1 for Cu(II) in Zn(II)-bis(diethyl-diselenocarbamate) was measured in the temperature range 1.5 < T < 33 K. From the T-dependence of T1 -1 the Debye temperature of the host crystal was obtained. The angular dependence of T1 -1 as well as the influence of the hyperfine interaction on T1 -1 are discussed. © 1974

TEM investigations of Ga(Sb,As) quantum dots grown on a seed layer of (In,Ga)As quantum dots

This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Peer Reviewe

Random matrix description of decaying quantum systems

This contribution describes a statistical model for decaying quantum systems (e.g. photo-dissociation or -ionization). It takes the interference between direct and indirect decay processes explicitely into account. The resulting expressions for the partial decay amplitudes and the corresponding cross sections may be considered a many-channel many-resonance generalization of Fano's original work on resonance lineshapes [Phys. Rev 124, 1866 (1961)]. A statistical (random matrix) model is then introduced. It allows to describe chaotic scattering systems with tunable couplings to the decay channels. We focus on the autocorrelation function of the total (photo) cross section, and we find that it depends on the same combination of parameters, as the Fano-parameter distribution. These combinations are statistical variants of the one-channel Fano parameter. It is thus possible to study Fano interference (i.e. the interference between direct and indirect decay paths) on the basis of the autocorrelation function, and thereby in the regime of overlapping resonances. It allows us, to study the Fano interference in the limit of strongly overlapping resonances, where we find a persisting effect on the level of the weak localization correction.Comment: 16 pages, 2 figure

Advanced cryo-tomography workflow developments - correlative microscopy, milling automation and cryo-lift-out

Cryo-electron tomography (cryo-ET) is a groundbreaking technology for 3D visualisation and analysis of biomolecules in the context of cellular structures. It allows structural investigations of single proteins as well as their spatial arrangements within the cell. Cryo-tomograms provide a snapshot of the complex, heterogeneous and transient subcellular environment. Due to the excellent structure preservation in amorphous ice, it is possible to study interactions and spatial relationships of proteins in their native state without interference caused by chemical fixatives or contrasting agents. With the introduction of focused ion beam (FIB) technology, the preparation of cellular samples for electron tomography has become much easier and faster. The latest generation of integrated FIB and scanning electron microscopy (SEM) instruments (dual beam microscopes), specifically designed for cryo-applications, provides advances in automation, imaging and the preparation of high-pressure frozen bulk samples using cryo-lift-out technology. In addition, correlative cryo-fluorescence microscopy provides cellular targeting information through integrated software and hardware interfaces. The rapid advances, based on the combination of correlative cryo-microscopy, cryo-FIB and cryo-ET, have already led to a wealth of new insights into cellular processes and provided new 3D image data of the cell. Here we introduce our recent developments within the cryo-tomography workflow, and we discuss the challenges that lie ahead. Lay Description This article describes our recent developments for the cryo-electron tomography (cryo-ET) workflow. Cryo-ET offers superior structural preservation and provides 3D snapshots of the interior of vitrified cells at molecular resolution. Before a cellular sample can be imaged by cryo-ET, it must be made accessible for transmission electron microscopy. This is achieved by preparing a 200-300 nm thin cryo-lamella from the cellular sample using a cryo-focused ion beam (cryo-FIB) microscope. Cryo-correlative light and electron microscopy (cryo-CLEM) is used within the workflow to guide the cryo-lamella preparation to the cellular areas of interest. We cover a basic introduction of the cryo-ET workflow and show new developments for cryo-CLEM, which facilitate the connection between the cryo-light microscope and the cryo-FIB. Next, we present our progress in cryo-FIB software automation to streamline cryo-lamella preparation. In the final section we demonstrate how the cryo-FIB can be used for 3D imaging and how bulk-frozen cellular samples (obtained by high-pressure freezing) can be processed using the newly developed cryo-lift-out technology