Cross relaxation effects

Just as in the COSY type of experiments this cross-relaxation effect is not restricted to protons, but can also involve heteronuclei the acronym HOESY (heteronuclear Overhauser effect) is used in these cases. This can be used, for example, to show that an anion such as IT1., is in close proximity to the ligands of the organometallic compound, as was carried out by Macchioni et al. with a 19F-xH HOESY experiment [24]. 

Similar results were obtained by De Shazer using a different detection technique, where laser oscillations in the sample were forced to develop from the narrow-band radiation, injected from a second small aperture laser into the sample laser cavity. The interionic transfer allowed the feeding of this narrow-band radiation by ions having frequencies outside this interval. The effeciency of energy extraction within the narrow bandwidth and the degree of depolarization of the laser oscillations parametrize the cross relaxation effects. 

F%. 12. Pulse sequences for indirect Ti measurements " (a) Inversion recovery with subsequent DEPT transfer, (b) Inversion recovery with double DEPT transfer and a series of 180°(X) pulses to suppress cross-relaxation effects, (c) Inversion recovery vrith double INEPT transfer. 

McGarvey and Schlick [49] observed (by both and F NMR) a two-component behaviour of the longitudinal relaxation in PVDF material which contains the modification a in its crystalline phase. The results have been interpreted by incorporating cross-relaxation effects. 

Interest in water at protein surfaces and other surfaces arises from a desire to understand structural, functional, and dynamic factors as well as their interrelationships. Nuclear magnetic resonance (NMR) spectroscopy provides both structural and dynamic information. This presentation will focus on dynamical aspects of the water-protein Interaction. In particular, the phenomenon of cross relaxation between the water and protein proton systems will be discussed and new evidence will be reported. Failure to recognize the importance of cross relaxation effects leads to incorrect conclusions about the dynamics of water at protein surfaces. 

This type of ENDOR is generally not so sensitive to experimental conditions such as temperature and microwave and rf power as is steady-state ENDOR. Marked peculiarities do exist, however. For example, for this type of ENDOR, depending on experimental conditions, the ENDOR response can be either an increase or a decrease in the EPR signal. Generally a decrease is the norm. In addition, some cross-relaxation effects can make the intensities and relative directions of the and v transitions anomalously different we have often found the transitions to be more intense, particularly at the higher (35 GHz) microwave frequency. 

Level Anticrossing and Cross-Relaxation Effects A. The Level Anticrossing Experiment Cross-Relaxation Effects Microwave Studies Radiofrequency Studies Lifetime Measurements VI. Coherence Experiments A. The Rotating Frame Free Precession Spin Echoes... 

T2 transvers relaxation time) The value Tz/Tj- = 5 has been assumed, where T(- is the correlation time (reciprocal spectral width) of light sources. The coherence parameter P represents the extent of random phase distribution, and the dispersion parameter W represents the degree of regular phase-modulation due to material dispersion (see text for definition). The cross relaxation effect has been neglected. 

In actual materials, there exists more or less the cross relaxation effect within an inhomogeneous broadening, which has been neglected in the previous consideration. Its effect in the transient four-wave mixing will be examined next. The model and basic equations representing the cross... 

Fig. 8 Effect of time dulation (D) of incoherent incident light on the correlation traces of transient degenerate four-wave mixing (a) without (T2/T3 0) and (b) with (T2/T3 = 0.2) cross relaxation effect. Other conditions are the same as in Fig. 7. Curves 1, 2, 3 correspond to D/t = 19, 38, 76, respectively.

It has been pointed out that, in a multi-level system where one energy level is optically connected with a set of closely spaced many levels, observation of T2 becomes essentially difficult with transient spectroscopy. The cross relaxation effect is considered to manifest a part of the specific feature of this type of multi-level system. 

Szabo A. Observation of hole burning and cross relaxation effects in ruby. Phys. Rev. B 1975 11 4512 517... 

---