Population transfer

We now make two coimections with topics discussed earlier. First, at the begiiming of this section we defined 1/Jj as the rate constant for population decay and 1/J2 as the rate constant for coherence decay. Equation (A1.6.63) shows that for spontaneous emission MT = y, while 1/J2 = y/2 comparing with equation (A1.6.60) we see that for spontaneous emission, 1/J2 = 0- Second, note that y is the rate constant for population transfer due to spontaneous emission it is identical to the Einstein A coefficient which we defined in equation (Al.6.3). 

Bardeen C J, Yakovlev V V, Wilson K R, Carpenter S D, Weber P M and Warren W S 1997 Feedback quantum control of molecular electronic population transfer Chem. Phys. Lett. 280 151... 

To add non-adiabatic effects to semiclassical methods, it is necessary to allow the trajectories to sample the different surfaces in a way that simulates the population transfer between electronic states. This sampling is most commonly done by using surface hopping techniques or Ehrenfest dynamics. Recent reviews of these methods are found in [30-32]. Gaussian wavepacket methods have also been extended to include non-adiabatic effects [33,34]. Of particular interest here is the spawning method of Martinez, Ben-Nun, and Levine [35,36], which has been used already in a number of direct dynamics studies. 

Population transfer model Herring Keyes [55H01, 60K01]... 

Population transfer experiments may be selective or nonselective. Selective population transfer experiments have found only limited use for signal multiplicity assignments (SSrensen et al, 1974) or for determining signs of coupling constants (Chalmers et al., 1974 Pachler and Wessels, 1973), since this is better done by employing distortionless enhancement by polarization transfer (DEPT) or Correlated Spectroscopy (COSY) experiments. However, nonselective population transfer experiments, such as INEPT or DEPT (presented later) have found wide application. 

How does magnetization transfer from H to a coupled C nucleus (polarization transfer or population transfer) affect the signal intensity of the C nucleus ... 

The laser parameters should be chosen so that a and p can make the nonadiabatic transition probability V as close to unity as possible. Figure 34 depicts the probability P 2 as a function of a and p. There are some areas in which the probabilty is larger than 0.9, such as those around (ot= 1.20, p = 0.85), (ot = 0.53, p = 2.40), (a = 0.38, p = 3.31), and so on. Due to the coordinate dependence of the potential difference A(x) and the transition dipole moment p(x), it is generally impossible to achieve perfect excitation of the wave packet by a single quadratically chirped laser pulse. However, a very high efficiency of the population transfer is possible without significant deformation of the shape of the wave packet, if we locate the wave packet parameters inside one of these islands. The biggest, thus the most useful island, is around ot = 1.20, p = 0.85. The transition probability P 2 is > 0.9, if... 

Enhancements between signals that are strongly spin-coupled to each other are best ignored as they are prone to another competing phenomenon, that of Selective Population Transfer (SPT). This makes it difficult to decide if any observed enhancement is down to a genuine NOE, or is merely an SPT. SPT... 

Many species of parasitic nematodes are maintained in the laboratory in host species in which they are not found in nature. This has the potential consequence that the laboratory population is, in some way, different from the natural population. Transfer and adaptation of a parasite from a natural host into a different species in the laboratory entails a process of selection. The selection will act on the trait ability to survive in a nonnatural host . Most of the parasite population may have had little, or indeed no, ability to survive in the non-natural host. Thus, at its most extreme form, this selection will have been for the very small proportion of the parasite population with the ability to survive in a non-natural host. A consequence of this is that the parasite population will have gone through a genetic bottleneck. 

The first term in Eq. (III. 10) is originated from the decay from v to v 1, while the second one, with the Boltzmann factor, is due to the thermally activated transition from v to v + 1. The vibrational population transfer, on the other hand, is only allowed to undergo the v —> v 1 transitions in the ladder model. Thus, the rate constant of the transfer is given by... 

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