Multipulse sequences

Figure 4. dj-vinyl acetate (MW=89) response curves derived from a long term multipulse sequence with a premixed dj-acetic acid + ethylene + oxygen feed. 

Figure 6.10 Ultrafast efficient switching in the five-state system via SPODS based on multipulse sequences from sinusoidal phase modulation (PL). The shaped laser pulse shown in (a) results from complete forward design of the control field. Frame (b) shows die induced bare state population dynamics. After preparation of the resonant subsystem in a state of maximum electronic coherence by the pre-pulse, the optical phase jump of = —7r/2 shifts die main pulse in-phase with the induced charge oscillation. Therefore, the interaction energy is minimized, resulting in the selective population of the lower dressed state /), as seen in the dressed state population dynamics in (d) around t = —50 fs. Due to the efficient energy splitting of the dressed states, induced in the resonant subsystem by the main pulse, the lower dressed state is shifted into resonance widi die lower target state 3) (see frame (c) around t = 0). As a result, 100% of the population is transferred nonadiabatically to this particular target state, which is selectively populated by the end of the pulse.

Fourier transformation of Eq. (1) shows that the higher the value of a, where 0 a re, the more intensity is found in replica pulses of an equispaced multipulse sequence with At = > (Fig. 2a). Parameter c controls the relative carrier phases between successive pulses of the sequence. 

Fig. 2. Optimisation of internal conversion with multipulse excitation, a) Experimental setup Coherent multipulse sequences are generated by periodic modulation of the spectral phases. The multipulse spacing b is optimised for maximal ratio IC/EET by an evolutionary algorithm, b) Histogram of optimal modulation 2re/viightfe (i.e. multipulse separation) by successive optimisations.

Application of a Multipulse Sequence to Electrodes and Microelectrodes of Any Geometry... 

In order to evaluate the conditions under which it is possible to achieve a stationary cyclic voltammogram, a key parameter is Nemst diffusion layer thickness, <5 , which was introduced in Sect. 2.2.1 for reversible processes when a single potential pulse is applied. It is possible to extend the definition of to a multipulse sequence, <5)f, as... 

The pulse sequence for ICP experiments appears simple a 90° proton pulse is followed immediately by a spin lock radio-frequency (rf) field of strength B that is phase shifted by 90° relative to the first pulse. By a spin-lock field is meant a strong rf field B that is on resonance with the given nucleus it keeps magnetization in a spin-locked orientation parallel to the B direction where the decay of magnetization is governed by T p. At present the strong continuous B field is replaced by multipulse sequences that are well known from other spin-lock experiments such as TOCSY, ROESY etc. Simultaneously,... 

The spin echo technique, which has many uses in NMR spectroscopy, has introduced us to our first example of a multipulse sequence 90y-x-180y-x-acquire. We will see another example below and many more examples in Chapters 12 and 13. 

The spin echo technique is a multipulse sequence used (among other things) to measure true T2 values. The spin inversion-recovery techniques is a multipulse 2D technique for measuring T values. 

The development of new ID and 2D pulse sequences enables the spectroscopist to obtain structure and dynamic information about systems that were previously very hard to study. As an example is reported in Fig. 3.2.13 the 2D spectrum of erythromycin A measured with the FIREMAT (Five p Replicated Magic Angle Turning ) technique [30]. The slow spinning speed of 390 Hz produces a spinning sideband pattern for each peak in one dimension, whereas a multipulse sequence in combination with a special processing method produces isotropic lines in the second dimension. 

Beyond the standard quadrupole echo experiment, multipulse sequences provide an alternative and versatile approach to measure transverse relaxation. The relaxation time constant T is obtained from a series of experiments with different pulse spacings t. Extending this sequence by n further 90 ... 

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