Electron depopulation

Electron depopulation of the donor and concomitant population of the acceptor in the complex results in a lowering of the vibrational frequencies in the IR spectra of the donor and acceptor moieties. Additionally, complex formation can decrease the symmetry of the donor/ acceptor dyad and can lead to increased IR intensity or the appearance of new bands. For example, in halogen/alkylbenzene complexes, the stretching frequencies of the halogens are lowered, as seen in the shift of chlorine band from 557 cm-1 in free chlorine to 530 cm-1 in the benzene complex, to 527 cm-1 in the toluene complex, and to 524 cm-1 in the p-xylene complex. Increases in the intensity of some of the arene bands are also clearly seen [23b]. 

Electrochemistry and redox chemistry provide possible ways of assessing the consequence of one-electron depopulation or population of orbitals. The M CO o spgcies suffer rapid M-M cleavage upon reduction (population of a ) or oxidation (depopulation of Ob) (20, 21). But cyclic voltammetry only reveals that the cleavage rate from the radical anion,... 

Fluorescence excitation spectra of fairly large molecules in a supersonic jet are simplified, vibrationally, due to depopulation of low-lying vibrational levels in the ground electronic... 

Zero field splitting (zfs) values in photoexcited triplets of primary donor bacteriochlorophyll a in photosynthetic bacteria are much lower than those found for vitro BChla triplets. There is a pronounced difference in kinetics of population and depopulation of the triplet sublevels as well. The differences have been attributed to the effect of BChla dimerization and it is now generally accepted that the primary electron donor in photosynthetic bacteria consists of a BChla dimer (special pair)(l- ). 

The increased cross sections for these three states are attributed to resonant electronic to vibrational energy transfer. Table 11.1 identifies the three atomic transitions and the resonant molecular transitions in CH4 and CD4. For example the rapid depopulation of the Na 7s state by CD4 is attributed to the Na 7s — 5d transition. To verify this assignment the cross section for the 7s — 5d transfer was measured for both CH4and CD4 by observing the 5d-3p fluorescence as well as the 7s-3p fluorescence. The 7s — 5d cross sections are 215 A2 for CD4 and 15 A2 for CH4. As shown by Fig. 11.16, the 7s CD4 cross sections is —240 A2 above the smooth dotted curve in good agreement with the 7s — 5d cross section. Similar confirmations were carried out for the other two resonant collisional transfers. 

Solid-state theories ascribe electron relaxation to the coupling of electronic spin transitions with transitions between lattice vibrational levels, or more generally with phonons. Disappearance (depopulation of a vibrational level) or creation (population of a vibrational level) of phonons modulate the orbital component of the electron magnetic moment. 

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