Crystallization setup

In this paper, we summarise our progress towards Is Lamb shift measurements on medium Z hydrogen-like ions produced in an electron beam ion trap (EBIT), where the X-ray emission is free from the problems of satellite contamination and Doppler shifts. In this context, we note that a measurement of the Is Lamb shift in hydrogen-like Mg11+ has been performed at the Livermore EBIT using a quasimonolithic crystal setup, and reaching a precision of 13% for the Lamb shift dominated by counting statistics [14]. With our setup, the... 

Figure 7 A schematic representation of a crystallization setup using a microdialysis button. The reservoir solution contains the precipitant, which slowly diffuses to the small depression in the button through the semi-permeable membrane.

On the other hand, modern macromolecular X-ray diffraction of crystals from biological materials (protein crystallography) is frequently carried out in a rotating-crystal setup [98,99] (Alexander [7], p. 51), (Warren [97], Chap. 7), (Glocker [ 100], p. 250) using plane 2D detectors in normal transmission setup. In this case the absolute scattering intensity of reflection hkl is given by the Darwin equation (cf. Warren [97], Eq. (4.7))... 

The temporal resolution of the two different crystal setups is determined by the pulse length of the pump pulse the remaining fundamental of the regenerative amplifier. The pulse length of the 1064-nm fundamental is about 100 ps for the harmonics the pulse lengths are about 70 and 60 ps for 532 and 355/266 nm, respectively. Thus, our temporal resolution is about 20 ps by applying standard deconvolution methods. The optical delay line (computer controlled) of the pump beam determines the maximum time scale of the experiment, about 8 ns, but it can be doubled to 16 ns by implementing a double-pass setup. 

Fig. 26.4 The hanging drop crystallization setup. A drop of a solution of protein with precipitant (==5-10 il) is suspended above a reservoir containing a much larger amount (=0.5-1.0 ml) of a more concentrated precipitant solution and the drop is allowed to equilibrate with the reservoir. Water moves from the less concentrated protein drop to the more concentrated reservoir solution via the vapour phase, causing the drop to shrink. The concentrations of protein and precipitant in the drop increase until the saturation point is reached and the protein starts to precipitate slowly. The precipitate is usually amorphous, but crystals will form in successful experiments.

With a very high concentration of 6-azaUMP in the crystallization setups, complex crystals can be induced and further stabilized by addition of Mg + ions (although the metal ion cannot be identified in the resulting electron density map). After a few days, however, ligand-free crystals will nucleate on top of the deforming complex crystals and grow at their expense (Fig- 9). 

It will be a little tricky but one can also try to purify by freezing I The sassafras oil is thrown into the freezer to chill. Safrole itself freezes at -14°C so anything that starts to freeze prior to that can be cold filtered in a prechilled vacuum filtration setup. The filtrate goes back in the freezer until -14°C is reached and the mother lode of safrole freezes up. This again is filtered cold but this time the frozen mass of safrole crystals are washed with some ice cold methanol or ethanol (preferably at -14°C) to wash away the unfrozen high-boiling constituents. 

An important method for producing semiconductor layers is the so-called molecular beam epitaxy (MBE) (see [3,12-14] and [15-19]). Here, atoms of the same or of a different material are deposited from the vapor source onto a faceted crystal surface. The system is always far from thermal equilibrium because the deposition rate is very high. Note that in this case, in principle, every little detail of the experimental setup may influence the results. 

Cyclopropyltriphenylphosphonium Bromide (5). The lactone salt is pyrolyzed by placing it in a round-bottom flask fitted with an adaptor attached to a vacuum source (aspirator is sufficient). The flask is heated (oil bath) to 180-190° for 48 hours. The residue is a virtual quantitative yield of the tan product, which may be crystallized from ethyl acetate giving cream crystals, mp 189-190°. An alternate setup is convenient if a drying pistol (Abderhalden) is available. The compound is placed in the pistol, which is then evacuated. Decalin (bp approx. 187°) is refluxed over the pistol to provide the heating source. The work-up is the same. 

Can one use STM to study spillover/backspillover phenomena and to confirm the origin of electrochemical promotion The answer is positive and the experimental setup used for the first demonstration of electrochemically controlled spillover/backspillover between a catalyst-electrode (Pt) and a solid electrolyte (p"-Al203) is shown in Figure 5.48.78,79 A polished Pt(lll) single crystal (lOmmxlOmmxlmm) was mounted on an appropriately carved polycrystalline p"-Al203 sample (20mmx20mmx3mm). 

The electrochemical behavior of single-crystal (100) lead telluride, PbTe, has been studied in acetate buffer pH 4.9 or HCIO4 (pH 1.1) and KOH (pH 12.9) solutions by potentiodynamic techniques with an RRDE setup and compared to the properties of pure Pb and Te [203]. Preferential oxidation, reduction, growth, and dissolution processes were investigated. The composition of surface products was examined by XPS analysis. It was concluded that the use of electrochemical processes on PbTe for forming well-passivating or insulating surface layers is rather limited. 

The typical experimental setup (here the experiment established at beamline G3/ HASYLAB [12] is shown) is outlined in Figure 5. The white synchrotron radiation is monochromatized by a double crystal monochromator using the Ge (311) reflection... 

Thermal desorption spectra of carbon monoxide on polycrystalline and on single crystal platinum are well known from experiments in the gas phase [48,49], The system is therefore appropriate to test the experimental setup. 

Figure 5.7 Setup for the inductive heating of single-crystal electrodes in controlled atmosphere.

Complete scattering patterns of samples with a complex single-crystal anisotropy can only be recorded in a texture setup (Chap. 9, Fig. 9.3). The samples must be rotated in order to scan the required fraction of reciprocal space. 

It should be clear that the Darwin equation with its special LoRENTZ-polariza-tion factor as reported by Warren ([97], Eq. (4.7)) is only valid for unpolarized laboratory sources and the rotation-crystal method. An application to different setup geometries, for example to synchrotron GIWAXS data of polymer thin films is not appropriate. 

Swirl and pour the crystals and solvent slowly, directly into the center of the filter paper, as if to build a small mound of product there. Slowly Don t flood the funnel by filling it right to the brim, and waiting for the level to go down. If you do that, the paper may float up, ruining the whole setup. 

---