Pulse Progressive saturation

A number of pulse-sequence methods are available for measurement of Ti values, and those most commonly used are the methods of saturation recovery (s.r.F.t.),69,70 progressive saturation (p.s.F.t.),71 inversion recovery (i.r.F.t.),72 and the Freeman-Hill modification of in-... 

C spin-lattice relaxation times of individual nuclei can also be measured by PFT 13C H experiments using a 90°, r, 90", r,... pulse train and noise modulation of the proton decoupling frequency. This method is known as progressive saturation [43] and is based on the following concept. 

The spin-lattice relaxation-time T, may also be measured by use of a 90°, f, 90° pulse sequence that employs decreasing values of f to produce a progressive saturation effect.173... 

Figure 8.2(c) is an inversion-recovery quadrupole echo pulse sequence, which is used to measure the Zeeman spin-lattice relaxation time,, with quadrupole echo detection [8,9,115]. Pre-saturation (Figure 8.2(d)) or progressive saturation (variation of the delay between transients) are also used to measure T. Notably, pre-saturation with spectral subtraction can separate the spectra of domains with different and is used to obtain the individual spectra of the amorphous and crystalline regions of semicrystalline polymers [8]. Also, Void and co-workers have recently presented methods involving selective inversion for the measurement of slow molecular reorientation, which provide an alternative to spin alignment or multidimensional methods [116]. 

Spectral resolution enhancement can be achieved by partial relaxation, which capitalizes on the different relaxation times, T, of the protons in a molecule (324). The partial relaxation experiment usually employs the inversion recovery pulse sequence [180°- r-90°-acquisition] (390), though progressive saturation (106) can also be employed. 

No measurable amount of CH4 was formed during the reaction of CO + H2 (1 4) pulses over Ru metal at temperatures of 300 and 370 K. While no CH4 was produced from the first pulse at the sample temperatures of 420 and 470 K, successive pulses gave rise to progressively increasing yields of methane and the CO(.d) --> CH4 conversion reached a saturation value of about 45 and 98% for the reaction temperature of 420 and 470 K, respectively. 

Electron spin relaxation times reflect both intramolecular and intermolecular dynamic processes. In favorable cases relaxation times can be estimated from progressive power-saturation measurements, but more accurate values can be obtained by pulsed time domain techniques. For metal ions with low-lying excited states the temperature dependence of relaxation times can be used to determine the energy of the excited state. ... 

The amount of amine adsorbed up to a given pulse was obtained by the summation of the single adsorbed quantities via the equation above reported. Plot of the total amount of amine adsorbed versus the total amine injected provides clear evidence of the progressive coverage of the sample surface. At saturation, the curve attained a plateau corresponding to the total amount of amine adsorbed. 

The SR pulse sequence is another way to measure Tj. It destroys any coherence among spins and saturates the bulk magnetisation to zero before it recovers progressively towards equilibrium. The SR experiment is similar to the IR experiment except that it starts with P pulses so that it saturates the... 

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