Resonance line width

Garnets have played an important role in the development of highly sophisticated microwave devices since the development of yttrium—iron garnet, yttrium iron oxide [12063-56-8]. The iron is strongly constrained to be trivalent in order to maintain electrical neutraUty in the crystal, which is essential for low microwave losses. Garnets have lower values of saturation magneti2ation than spinels, but provide superior performance in microwave devices because they have a narrower resonance line width. 

Potzel et al. [60] used a Ga/ZnO single crystal source in combination with a single crystal absorber of natural ZnO and observed a resonance line width of 0.36 0.04 pm s for the 93.3 keV transition in Zn (at 4.2 K). This, after correction for finite absorber thickness, equals, within the limit of error, the minimum observable line width as deduced from the lifetime of 13.4 ps for the 93.3 keV state. The spectra observed by these authors are shown in Fig. 7.23. 

The price to pay for getting the higher intermediate frequency in such a convenient way would be the less clock-jitter tolerance, so that the apparent resolution of the resonance line can be degraded compared with that obtained in the conventional detection scheme. For this reason, we demonstrated the high-resolution liquid-state NMR experiment, in which the resonance line width was on the order of Hz. In fact, we observed a drift of the peak position when we used a less stable clock... 

The ratio of the 3 dB resonance line width, A23dB, to the free spectral range is known as the finesse ... 

Several general observations can be made from the spectra and the calculated ESR parameters. First, the Na+- smectites possess narrower resonance line widths than the Ca +-smectites, with the exception of the saponite. Since Ca +-smectites, unlike Na+ -smectites, do not disperse into individual platelets in aqueous suspension, the Na+-smectite films formed by drying suspensions onto a smooth flat surface have the silicate surfaces more perfectly oriented in the plane of the film. As a result, less angular variation of the z-axis of Cu + relative to the plane of the film would narrow the spectra. One can see evidence of hyperfine splitting in the gj component of the Na+-smectite spectra, but not in the Ca +-smectite spectra. Saponite, unlike the other smectites, has very similar spectral linewidths for the Na+ and Ca + form (Figure 16). Since this Na+-saponite sample does not disperse completely in water (Table II), the alignment of Na+-saponite platelets in the clay film may be no better than that of the Ca +-saponite. 

The SjN ratio increases with the square-root of the number of scans, provided that the NMR signals are perfectly reproducible (except for the receiver noise). In EEC, this is not always true due to the main field instabilities, which often exceed the natural resonance line-width of the sample. In such cases, the rule applies well to the starting portion of the FIDs but not... 

Nuclear magnetic resonance measurements of methane adsorbed to various coverages on titanium dioxide have been made by Fuschillo and Renton 16). At a coverage of 0.95 monolayer and at 20.4°K, the X-point for solid bulk methane, these authors observed an abrupt change in the proton resonance line width, presumably due to translational and rotational diffusion of methane molecules. For pure, bulk methane no change has been observed in the line width at the X-point. 

Considerations of the signal-to-noise ratio usually dictate the use of the technique of narrow-banding in nuclear resonance. The modulation magnetic field is reduced to small amplitude compared to the resonance line width as shown in Fig. 3. 

The effect of atomic motion in the solid state on nuclear resonance line width is illustrated by the behavior of Na resonance from NaCl as a function of temperature 97). In Fig. 9 is shown the variation of the Na line width with temperature for pure NaCl and NaCl doped with an atomic fraction concentration of 6 X 10 of CdCU. As discussed in Section II,A,2 the low-temperature, rigid-lattice line width will narrow when the frequency of motion of the nuclei under observation equals the line width expressed in sec.-. The number of vacancies present should be equal to the concentration of divalent impurities and the jump frequency of Na+ is the product of the atomic vacancy concentration and the vacancy jump frequency... 

Van Vleck (73) and Anderson and Weiss 1B7) have considered the narrowing effect of exchange interactions on the resonance line width. These authors... 

Fig. 5. The 13C nuclear magnetic resonance line widths of the (enriched) choline methyl resonances in dipalmitoylphosphatidylcholine (A) and in dielaidoylphosphatidylcholine (O), as a function of temperature. Spectra taken at 90.5 MHz similar results were also obtained at 25.2 MHz. Note that the higher-melting lipid, dipalmitoylphosphatidylcholine, shows a readily observable enhanced line broadening at temperatures TU 32°C, corresponding to the onset of the lateral phase separation. (Data from Ref. 4.) [Reprinted with permission from P. Brulet and H. M. McConnell, J. Am. Chem. Soc., 98, 1314 (1977). Copyright by American Chemical Society.]...

Fig. 1. Temperature dependence of the proton resonance line width (Av) in vulcanized natural rubber cured for 30 (A) and 90 (O) minutes (adapted from Ref.18))...

Turning now to the polyamide 6-6 Nylon, Slichter (1958b) observed a narrowing of the proton resonance line width from about 75 to 125° C, but there were no indications from the specific heat data of this in... 

Slichter, (1959) found that a narrowing of the proton resonance line width occurred 10—20° C above Tg in the case of polyisobutylene and natural rubber but closely at Tg in the case of atactic polypropylene. The two room temperature transitions in polytetrafluoroethylene, which are so clearly visible in the specific heat-temperature curve, Fig. 12, were found by Slichter (1958a) in a fluorine nucleus magnetic resonance study to cause a drop in the second moment with rise of temperature, but the whole effect occurred over the wide temperature range of 225 to 320° K. The slight bulge" in the specific heat-temperature curve of polymethyl methacrylate from 130 to 180° K, Fig. 13, might possibly be correlated with the drop in the NMR second moment between 150° and 200° K found by Powles (1956). 

Fig. 6.2. Illustration of the frequency-time dependences of pump and Stokes pulses in three different CRS excitation pulse schemes and their corresponding spectral resolution of Raman shifts. A Using a pair of transform-limited femtosecond pulses of broad spectral and narrow temporal widths results in a broad bandwidth of Raman shifts that exceeds the line width of a single Raman resonance. B Using transform-limited picosecond pulses of broad temporal and narrow spectral width readily provides high spectral resolution matching the Raman resonance line width to be probed. Selection of a Raman resonance shifted by AQr is achieved by tuning the frequency of one of the laser beams by the same amount. C Spectral focusing of a pair of identically linear chirped pump and Stokes femtosecond pulses results in a narrow instantaneous frequency difference in the CRS process, thus also providing narrow-bandwidth CRS excitation. Selection of a Raman resonance shifted by AQr is achieved by adjusting the time delay At between the pulses. Shifted pulses in (B) and (C) are depicted hatched...

As shown in Fig. 6.2B, this can be directly achieved by using transform-limited pump and Stokes pulses, of which the spectral bandwidth matches the Raman resonance line width to be probed [37]. The temporal width of the pulses is typically 5ps, corresponding to a spectral width of 2.9cm. A frequency-resolved CRS spectrum is obtained by tuning the wavelength of... 

Illustrative applications include the determination of stereochemical structure, and conformational preferences. 9 Another application is the determination of chemical composition and chemical sequence distributions in copolymers. A final example is the study of relaxation processes and molecular motions in general, including the determination of transition temperatures from changes in resonance line widths. 

Cu(en), Fig. 3a. Effective g-factor components are gy = 2.31, gi = 2.06, these do not show the temperature dependence whereas the resonance line width sharply increases when temperature is reduced to T < 15 K. Such... 

For Cu(en) and Cu(nad) compounds the short-range magnetic order is achieved in low-temperature part of the investigated temperature region. At these temperatures the effective g-factor components are nearly constant whereas the resonance line width increases dramatically when the temperature decreases. 

The melting transition of the daunomycin poly(dA-dT) complex can also be monitored at the nucleic acid resonance line widths and the data for the adenosine H-8 resonance are plotted in Figure 28. The resonance is very broad at temperatures below the melting transition of the complexes (dashed curves in Figure 28) indicative of stiffening of the synthetic DNA by the bound anthracycline ring. 

The width AH0 of the resonance absorption curve measured at half peak power - the 3 dB resonance line width - should in general be as small as possible since this implies a narrow range of frequencies over which strong interaction with the ferrite can occur however, there are certain broad-band applications where this would not be the requirement. There are two main contributions to the linewidth ... 

Owing to the special form of the eigenwave functions for t] f=0, and in accordance with the absence of first-order Zeeman effect, it may be shown that the magnetic dipolar contribution to nitrogen resonance line width is very small33,34). Lines are consequently narrow for many of the compounds studied, a very convenient feature when weak effects, like the Stark effect, are to be studied35). 

The positive one-bond isotope effects on nitrogen are larger for the Z isomer than for the E isomer, also due to intramolecular hydrogen bonding. A linear relationship has been found between 2AC(ND) and SH of NH for both E and Z isomers. The Z isomers show the narrower 15N resonances (line-widths) also as a result of hydrogen bonding. 

Figure 22 Effect of electron self-exchange reaction (Fe /Fe ") on oxidized heme methyl resonance line widths of Pseudomonas aeruginosa ferricytochrome C551, 25 °C. (a) 100% Fe , (b) 98% Fe L This ESE reaction is fast on the NMR timescale ( 10 s )...

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