P+ electronic transition

Fig. 2. Probable electronic band structure of unreacted crystalline explosive versus direction through the shock front. The pressure fore and aft the front are, respectively, Pq and P electronic transitions, transport, and tunneling are also shown.

FIGURE 16.6 An example of the normal Zeeman effect. The S P electronic transition is split into a triplet as a magnetic field separates the individual levels in the P excited state. 

Avouris P, Bozso F and Walkup R E 1987 Desorption via electronic transitions fundamental mechanisms and applications Nucl. Instrum. Methods Phys. Res. B 27 136-46... 

Walker G C, Maiti S, Cowen B R, Moser C C, Dutton P L and Hochstrasser R M 1994 Time resolution of electronic transitions of photosynthetic reaction centers in the infrared J. Phys. Chem. 

All of these time correlation functions contain time dependences that arise from rotational motion of a dipole-related vector (i.e., the vibrationally averaged dipole P-avejv (t), the vibrational transition dipole itrans (t) or the electronic transition dipole ii f(Re,t)) and the latter two also contain oscillatory time dependences (i.e., exp(icofv,ivt) or exp(icOfvjvt + iAEi ft/h)) that arise from vibrational or electronic-vibrational energy level differences. In the treatments of the following sections, consideration is given to the rotational contributions under circumstances that characterize, for example, dilute gaseous samples where the collision frequency is low and liquid-phase samples where rotational motion is better described in terms of diffusional motion. 

Measure, approximately, the wavenumbers of the P-branch and i -branch rotational transitions in the 0-0 band of the electronic transition of CuH in Figure... 

Fig. 5 Schematic representation of the electronic transitions during luminescence phenomena [5]. — A absorbed energy, F fluorescence emission, P phosphorescence, S ground state. S excited singlet state, T forbidden triplet transition.

It is notable that pyridine is activated relative to benzene and quinoline is activated relative to naphthalene, but that the reactivities of anthracene, acridine, and phenazine decrease in that order. A small activation of pyridine and quinoline is reasonable on the basis of quantum-mechanical predictions of atom localization encrgies, " whereas the unexpected decrease in reactivity from anthracene to phenazine can be best interpreted on the basis of a model for the transition state of methylation suggested by Szwarc and Binks." The coulombic repulsion between the ir-electrons of the aromatic nucleus and the p-electron of the radical should be smaller if the radical approaches the aromatic system along the nodal plane rather than perpendicular to it. This approach to a nitrogen center would be very unfavorable, however, since the lone pair of electrons of the nitrogen lies in the nodal plane and since the methyl radical is... 

The recombination should be governed by the same selection rules as spectroscopic transitions. Let us consider the recombination of an oxygen ion 2s2 2p3 4S°. When one p electron is added to the 4S ion we expect to obtain one of the states 5P and 3P. However, if the 2s2 2p4 state of the atom is obtained, it can only exist in the states 3P, lD, or lS. Thus the recombination can only give 2s2 2p4 3P. Sometimes the selection rules are not strictly valid. In this case, however, no transitions 2s2 2p3 4S° nx - 2s2 2p4 XD or lS have been observed by the spectros-copists (57) which shows that in this case the selection rules are strictly valid. 

In the next chapter we look at the intensities of d-d electronic transitions. We shall see that transitions between terms of the same spin-multiplicity are much more intense than those involving a change of spin. It is for this reason that our focus in the present chapter has been on the former. We have seen that for d d , d and configurations in octahedral or tetrahedral environments, there is only one so-called spin-allowed transition. For

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Symbols are used to represent aspects of electronic stracture in atoms, and the symbolism is augmented as a student progresses through different levels of study e.g. those used to represent electron shells (K, L, M...) for orbital types (to s, p, d, f, sp, etc. in atoms a, tt, 8, etc. in molecules) for description of electronic states ( Pi, So, A2g, Tig, Cgt g, T2g). Introducing the added complexity of the time dimension, electronic transitions can be represented as shifts between shells, orbitals or states. 

Figure 4. The calculated spectrum of the complex after a Lorentzian band convolution. Region I is dominated by bridging-sulfur-to-iron CT transitions, while region II is mostly due to organic-sulfur-to-iron electron transitions. Regions I and II are explained in a MO diagram. The vertical lines correspond to the experimental bands observed in the absorption spectrum of the [Fe2 (J. - S2) P o - CqH4S) ) ] complex, from Reference 1.

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