Phase rotation technique

Microwave Hall experiments have been performed in our laboratory.16 They have shown that the mobility of charge carriers in semiconductors can be measured quite reliably even if the semiconductors are only available in the form of a powder. The measurement technique itself is relatively complicated and involves, for example, rectangular waveguides, which can be rotated against each other on opposite sides of the sample to monitor the phase rotation. In the two-mode resonator, two modes of... 

Termination rate constants for alkyl and benzyl radicals in solution range between 109 and 1010 M 1 sec-1.85 These rates correspond quite closely to that calculated for a diffusion-controlled reaction, about 8 x 109 M x sec-1 for the common solvents at room temperature.86 Gas-phase rotating sector results are similar a newer method, however, shows that in the gas phase the rotating sector technique overestimates termination rates. Recombination is fastest for methyl radicals (1010,5 M-1 sec-1) and slower for others (-CF3, 109-7 at 146°C ... 

Another example of the application of gas-phase NMR techniques to conformational equilibria is the investigation of conformational effects on the relative maxima in the N-0 bond internal rotation potential function in primary nitrites of one to five carbon atoms [27,22]. Alkyl nitrites (ONOR) exist as mixtures of syn and anti conformers which differ in the orientation of the alkyl group with respect to the nitrosyl group. 

The relevance of C-H- - -tt interactions in many supramolecular systems has made them the subject of specific monographies [6]. In these interactions the acceptor is constituted by the region where the ir-electrons are located (double, triple bonds, or aromatic ir-rings). The best known ir-acceptors are phenyl rings, double and triple C-C bonds, cyano groups, and pyridyl rings. The hydrogen bonded nature of the C(sp)-H- n interactions in the acetylene acetylene [102] and HCN-acetylene [103] complexes has been established by a combination of experimental techniques (gas-phase rotational spectroscopy... 

Another type of ollipsomeier uses a phase modulation technique. In this technique, a rotating quarier-... 

Fig. 2.26 Schematic representation of the principle of the phase-shifting technique by rotation of the complex plane coordinate.

However, application of the above technique can be problematic when strong solution-phase absorption obscures weak bands of a surface species. To overcome this limitation, the phase rotation approach [263] can be used. Phase-sensitive detection such as with a lock-in amplifier (LIA) provides two signals the signal that is in phase IP) and the signal that is out of phase (the quadrature, Q) with the external perturbation [264]. These quantities can be represented at each... 

Wes] X-ray diffraction studies (Laue, rotation techniques), optical microscopy, chemical analysis W2pe4C phase containing alloys... 

Abbreviations used ACRT - Accelerated Crucible Rotation Technique, CZG - Czochralski Growth, EV Growth, HPS-High-pressure Solution Growth, HYG - Hydrothermal Growth, LPE-Liquid Phase Epitaxy. 

Raman scattering is normally of such very low intensity that gas phase Raman spectroscopy is one of the more difficult techniques. This is particularly the case for vibration-rotation Raman spectroscopy since scattering involving vibrational transitions is much weaker than that involving rotational transitions, which were described in Sections 5.3.3 and 5.3.5. For this reason we shall consider here only the more easily studied infrared vibration-rotation spectroscopy which must also be investigated in the gas phase (or in a supersonic jet, see Section 9.3.8). 

One final technical improvement in soHd-state nmr is the use of combined rotational and multiple pulse spectroscopy (CRAMPS) (2), a technique which also requires a special probe and permits the acquisition of high resolution H and X nucleus nmr from soHds. The combination of these methods permits adapting most of the 1-D and 2-D experiments previously described for Hquids to the soHd phase. 

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