Magnetic field irradiating

The most obvious merit of the technique being described is that the interferometer has great inherent accuracy combined with the high sensitivity and resolution (see below). Additionally, a few other advantages of this method must be mentioned. Thus, LICRM needs no calibration, and the mechanical contact of a specimen with the measuring scheme is excluded. It means that the measurement process itself does not affect the result obtained. LICRM is an inertia-less instrument. The linear dependence between deformation and signal characteristics is retained at any displacement (deformation), and the continuous information of the indicated types can be obtained in the course of the experiment. Insensitivity of a laser beam to the external influence, such as electric and magnetic fields, irradiation, etc., is also essential in some cases. 

Figure B2.4.6. Results of an offset-saturation expermient for measuring the spin-spin relaxation time, T. In this experiment, the signal is irradiated at some offset from resonance until a steady state is achieved. The partially saturated z magnetization is then measured with a kH pulse. This figure shows a plot of the z magnetization as a fiinction of the offset of the saturating field from resonance. Circles represent measured data the line is a non-linear least-squares fit. The signal is nonnal when the saturation is far away, and dips to a minimum on resonance. The width of this dip gives T, independent of magnetic field inliomogeneity.

Nuclear magnetic resonance, NMR (Chapter 13 introduction) A spectroscopic technique that provides information about the carbon-hydrogen framework of a molecule. NMR works by detecting the energy absorptions accompanying the transitions between nuclear spin states that occur when a molecule is placed in a strong magnetic field and irradiated with radiofrequency waves. 

Depending on how the secondary magnetic field is applied, there are two fundamentally different types of spectrometers, namely, continuous wave (CW) and pulse Fourier transform (PFT) spectrometers. The older continuous wave NMR spectrometers (the equivalent of dispersive spectrometry) were operated in one of two modes (i) fixed magnetic field strength and frequency (vi) sweeping of Bi irradiation or (ii) fixed irradiation frequency and variable field strength. In this way, when the resonance condition is reached for a particular type of nuclei (vi = vo), the energy is absorbed and... 

The proton experiment is a so-called single channel experiment the same channel is used for sample irradiation and observation of the signal, and the irradiation frequency is set (automatically) to the resonance frequency of the protons at the magnetic field strength used by the spectrometer. 

Other quinoline A-oxide derivatives have been examined. A 1,3-oxazepine is the major product of irradiation of 2-cyanoquinoline A-oxide whereas lactam formation predominates on irradiation of 4-methylquinoline N-oxide in aqueous ethanol.60 Lactam formation has been shown to be influenced by an external magnetic field and on this basis it has been proposed that the first step in this transformation is the formation of an excited radical-ion pair.61 1,3-Oxazepines undergo further reaction on prolonged irradiation. The synthesis of 4-substituted indoles, for example, has been accomplished in this way by irradiation of 5-substituted quinoline A-oxides.62... 

The external Hamiltonian Hext(t) described above contains in the high-field approximation (taking out the dependency of the external static magnetic field) the rf irradiation Hamiltonian of the form... 

Techniques have been developed for measurements of (T) down to liquid helium temperatures with the sample under various external perturbations such as hydrostatic pressure (Chap. 22), light irradiation (Chap. 30) and high magnetic fields (Chap. 23). 

Fig. 10 57Fe Mossbauer spectra of (bpym, Se) recorded at 4.2 K in zero-field after irradiation of the sample (a) and in a magnetic field of 50 kOe (b). Mossbauer subspectra correspond to LS in [HS-LS] (grey), HS in [HS-LS] pairs (light grey), HS in [HS-HS] pairs (dark grey)...

Important information relating to the intramolecular interaction in dinuclear units of [Fe(phdia)(NCS)2]2(phdia) can be drawn from the study of the LIESST effect at low temperature. The Mossbauer spectrum recorded at 4.2 K after slow cooling reveals 16.0% of HS and 84.0% of LS species (Fig. 17a). The spectrum recorded after the irradiation (1=488 nm) of the sample for one hour at 4.2 K shows an increase of the intensity of the HS doublet up to 25.0% (Fig. 17b). The spectrum recorded subsequently in a magnetic field reveals no [HS-HS] pairs it consists of 50.0% of [HS-LS] and 50% of [LS-LS] pairs (Fig. 17c). This is further evidence of the inherent stability of mixed pairs in [Fe(phdia)(NCS)2]2(phdia). ... 

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