Pulse separation time

In electron spin echo relaxation studies, the two-pulse echo amplitude, as a fiinction of tire pulse separation time T, gives a measure of the phase memory relaxation time from which can be extracted if Jj-effects are taken into consideration. Problems may arise from spectral diflfrision due to incomplete excitation of the EPR spectrum. In this case some of the transverse magnetization may leak into adjacent parts of the spectrum that have not been excited by the MW pulses. Spectral diflfrision effects can be suppressed by using the Carr-Purcell-Meiboom-Gill pulse sequence, which is also well known in NMR. The experiment involves using a sequence of n-pulses separated by 2r and can be denoted as [7i/2-(x-7i-T-echo) J. A series of echoes separated by lx is generated and the decay in their amplitudes is characterized by Ty. ... 

It is also possible to carry out three pulse electron spin echo experiments in which the second 180° pulse is essentially divided up into two 90° pulses separated by another experimentally variable time, T. If simultaneous modulation from two different nuclei is encountered it is possible to suppress one of these by carrying out a three pulse experiment and selecting an appropriate value of the first pulse separation time, t, to suppress one of the modulation frequencies. This is found to be particularly valuable in studying zeolite systems where modulations from both aluminum nuclei in the zeolite lattice and deuterium nuclei from water adsorbate molecules are encountered. 

One useful approach to the description of internal motion is to follow time dependence of the ensemble-average mean-squared displacement, Z, along the laboratory frame gradient axis as tl PGSE pulse separation time, A, is varied. The characteristic behaviour of as respectively dependent on 1/4 1/2 various time regimes represents a signature for... 

The ground state hyperfine structure splitting of Be was measured by optical pumping and rf transitions between suitable (M/, Mj) substates in magnetic fields of roughly 0.7-0.8T. The respective transitions were induced with two coherent rf pulses of 0.S sec duration separated by 19 sec. This Ramsey interference method provides signal linewidths dominated by the pulse separation time. The obtained magnetic hyperfine interaction constant of... 

The pulse separation time between successive light pulses is one of the important parameters during PIV measurements. For a velocity magnitude in jc-direction u, pulse separation time At,... 

Hence, there is an optimum pulse separation time, Af pj, at which the combined error because of residual error magnitude and loss of image pairs is minimum. This is found iteratively by slowly increasing the pulse separation time until the number of outliers within the vector map increases. The normalized strength of displacement correlation can also be optimized with respect to pulse separation time. 

L = FID liquid signal intensity Mg = initial magnetization Ps,y R, A) = average displacement propagator P = permeability q = diffusion wavevector defined as 2k) yG5 R = distance diffused by a spin S= amplitude of solid component in FID S = chemical shift 5 = FID solid signal intensity S q, A) = stimulated echo amplitude q = pulse separation time T2 = transverse relaxation time VI/= width of lamellar regions A = diffusion time Y= gyromagnetic ratio. 

Fig. 6. The generalized Jeener-Broekaert three pulse sequence. Note that FT of the solid echo and the alignment echo starts at times delayed by the pulse separation r, after the second and third pulse, respectively...

Linearly polarized, near-diffraction-hmited, mode-locked 1319 and 1064 nm pulse trains are generated in separate dual-head, diode-pumped resonators. Each 2-rod resonator incorporates fiber-coupled diode lasers to end-pump the rods, and features intracavity birefringence compensation. The pulses are stabilized to a 1 GHz bandwidth. Timing jitter is actively controlled to < 150 ps. Models indicate that for the mode-locked pulses, relative timing jitter of 200 ps between the lasers causes <5% reduction in SFG conversion efficiency. 

Jeener s idea was to introduce an incremented time ti into the basic ID NMR pulse sequence and to record a series of experiments at different values of second dimension to NMR spectroscopy. Jeener described a novel experiment in which a coupled spin system is excited by a sequence of two pulses separated by a variable time interval <]. During these variable intervals, the spin system is allowed to evolve to different extents. This variable time is therefore termed the evolution time. The insertion of a variable time period between two pulses represents the prime feature distinguishing 2D NMR experiments from ID NMR experiments. 

Elution with salt pulses A multiple step elution is performed by the introduction of, for example, 5%, 10%, 25%, 50%, and 100% of 1.5 M sodium chloride in 19 mM phosphate buffer (pH 2.5) containing 5% methanol. Each step is for 10 min and run at 0.5 mL/min. This elution method compromises analytical system dimensionality, as the peak capacity of the ion-exchange chromatography (IEX) step is equal at most to the number of salt steps. However, in the second dimension only one or two columns are needed and there is no particular limitation in the second dimension separation time as peptides are eluted in portions in a controlled manner. However, the number of salt steps is limited by the total analysis time. In this case the multidimensional system is relatively simple. 

Figure 10.3 (a) Chiral train of femtosecond pulses, separated by a constant time period r. The... 

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