High spectral density

Most of the basic ideas of atomic or molecular state selection by optical means were formulated near the advent of the laser (e.g. Kastler, 1950, and Dehmelt and Jefferts, 1962). However, widespread application of the technique only took place in the late 1970s and early 1980s with the availability of dependable tuneable CW and pulsed lasers. Only laser radiation carries a sufficiently high spectral density for significant manipulation of the thermal population of atomic (or molecular) levels in a beam. 

Our calculations show that these second order terms are important for a quantitative description of nonadiabatic systems. This is demonstrated in the pyrazine S1/S2 system, where a reduced 4-mode model provides a qualitative picture with the main peaks of the spectrum in the correct places. The addition of second order terms and all degrees of freedom, results in the correct spectral envelope also being produced by the model. Also in the allene A/B system, the second order terms are required, not only for the correct description of the Duschinsky rotation in the excited state, but also for the high spectral density between the two bands. Even in the butatriene X/A system, in which second order terms play a minor role in the description of the spectral band, the inclusion of these terms means that the ab initio data could be taken with minimal adjustment, whereas a reduced dimensionality model required significant adjustment of the expansion parameters. 

It is easy to see that the monotonous decay is the direct consequence of the fact that the ensemble of quantized modes of the free space is characterized by very high spectral density p cop, —> oo and has the... 

In a pragmatic way, this assumption as well as others made in our theoretical approach of the far infrared results, can be justified a posteriori in view of the very good qualitative agreement of the behaviour of the low and high spectral densities with the predicted one. Let s also stress that computer simulation indicates that the decoupling approximation works amazingly" well (see for instance Steele work on that topic). 

Current research aims at high efficiency PHB materials with both the high speed recording and high recording density that are required for future memory appHcations. To achieve this aim, donor—acceptor electron transfer (DA-ET) as the hole formation reaction is adopted (177). Novel PHB materials have been developed in which spectral holes can be burnt on sub- or nanosecond time scales in some D-A combinations (178). The type of hole formation can be controlled and changed between the one-photon type and the photon-gated two-photon type (179). 

MIM or SIM [82-84] diodes to the PPV/A1 interface provides a good qualitative understanding of the device operation in terms of Schottky diodes for high impurity densities (typically 2> 1017 cm-3) and rigid band diodes for low impurity densities (typically<1017 cm-3). Figure 15-14a and b schematically show the two models for the different impurity concentrations. However, these models do not allow a quantitative description of the open circuit voltage or the spectral resolved photocurrent spectrum. The transport properties of single-layer polymer diodes with asymmetric metal electrodes are well described by the double-carrier current flow equation (Eq. (15.4)) where the holes show a field dependent mobility and the electrons of the holes show a temperature-dependent trap distribution. 

The various symbols have the same meaning as before while the spectral density /csa(A),d(ffla) will be discussed in Section 4. For the moment, let us state that these cross-correlation rates can play a role only if the csa mechanism is important (i.e. for non-aliphatic carbons but certainly not for protons) and if measurements are performed at high... 

---