Donor transitions

We consider first the OS of the donor electron transitions corresponding to a single valley. With the axis orientation used in Hamiltonian (5.5), the matrix elements for transitions from the Is state to odd-parity states with m = 0 are non-zero when the electric vector (polarization vector) of the radiation is parallel to the z axis similarly those for transitions from the Is state to odd-parity states with m = 1 are non-zero when the electric vector is perpendicular to the 2 axis. The one-valley OSs are denoted accordingly as /// and / i. When considering the multi-valley degeneracy, it can be shown that for an arbitrary choice of the polarization vector, the OS for transitions from the Is (Ai) ground state to the odd-parity states with m = 0 is /o = fjj and those for transitions from the Is (Ai) ground state to the odd-parity states 

The energies of the final state (meV) are indicated. The OSs given by Clauws et al. [16] have been multiplied by 1000 for an easier comparison with those of [7], where this factor had already been included. The values in parentheses are normalized to 100 for the Is (Ai) — 3p transition 

The EMA OSs are given in Tables 5.20 (silicon) and 5.21 (germanium) for the screened potential of Hamiltonian (5.5). The agreement between the results based on non-variational calculations (a) and those based on variational calculations (b) is remarkable, except for the highly excited donor states in germanium. 

One can note that contrary to the np transitions, the variation with n of the OSs to the n/ levels is not monotonous and that the OS to 5/o is larger than that to 4/o. The calculated OS to Qf i is very small in silicon and the predictive value of the above calculation is attested by the absence in the donor spectra of this crystal of a line that could be attributed to a transition to this state. 

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Typical three-electron-donor transition-metal fragments (/2c, 25) are the (i)5-C5Hs)Ni and the (CO)3Co groups, which form mononuclear complexes with 3. However, 3 can also hold two metal moieties donating (1 + 2), (2 + 2), (2 + 3), and (3 + 3) electrons because slightly antibonding orbitals in the triple-decker complexes are then occupied. The planar ligands 5, 6, 7, and 8 with the formal acceptor capacities of 4, S, and 6 electrons should only exist in dinuclear complexes when stabilized by a pair of (2 + 2), (2 + 3), and (3 + 3)-electron-donor moieties (7). 

We may generalize the results and conclusions of the stability ruler by noting that alkali metal and alkaline earth metal ions, lanthanides, and AP+ prefer oxygen donors transition metal ions, oxygen and nitrogen donors and the heavy metal ions, nitrogen and sulfur donors. For amplification of this topic, (see Hard Soft Acids and Bases). 

Chiswell, B. Chemistry of multidentate ligands containing heavy Group VA donors. Transition Metal Complexes of Phosphorus, Arsenic and Antimony Ligands. McAuliffe, C. A., Ed., Macmillan London, Chapter 4, 1973, 269-307. 

We summarize below how we went about modeling EET in the neutral RC based on our model for EET in molecular aggregates. The most significant feature that differentiates the oxidized RC from the neutral reaction center, and any previously reported energy transfer systems we are aware of, is that the acceptor is a dimeric radical. Therefore, the focus of the problem was to determine the electronic energies and origins of the electronic transitions of the oxidized special pair acceptor and to quantify the electronic coupling between each of these relevant transitions and the donor transitions. 

Table 5.11. Calculated energies (meV) of the first donor transitions in GaN for different chemical donors [42]...

Table 5.20. Calculated OSs of shallow donor transitions from the Is (Ai) state in silicon...

Fig. 6.43. Magnetic-field tuned PTI spectrum at LHeT of Si-doped GaAs with Nd — Na 5 X 1014 at cm-3 at (a) a laser wavelength of 118.8 pm (84.18cm 1 or 10.44 meV) and (b) a laser wavelength of 46.2 pm (216.5 cm-1 or 26.84meV). The final states of most of the donor transitions observed are metastable states (the high-field-limit labelling is used with the parentheses omitted) (after [128]). Copyright 1990, American Institute of Physics...

After several reports between 1965 and 1980, no new information has been published on the spectroscopy of donors in GaP. Odd-parity transitions from the ground to excited states associated with the lowest X band for the Si, S and Te donors have been reported in the 55-100 meV ( 440-810cm-1) spectral domain [10,39,196,223]. The spectra are superimposed on the two-phonon spectrum of GaP and the FWHMs of the absorption lines at LHeT are - ()Ai meV. LHeT photoconductivity measurements in the photoionization region of shallow impurities in GaP revealed dips due to electronic transitions accompanied by the emission of LA(X) and LO (r) phonons with energies of 404 and 254 cm 1, respectively, and they have contributed to the understanding of the donor spectra [222]. LHeT transmission spectra of GaP Si samples at LHeT showing Si donor transitions are displayed in Fig. 6.45. 

The number of donor transitions observed in GaP is limited and some attributions can differ, but line 2p i is observed for all the donors and its position is taken as a reference. The energies of these transitions are given in Table 6.38. 

Table 6.38. LHeT positions (meV) of donor transitions observed in GaP samples, labelled by the final state of the transition...

Other transitions have been observed in the Se and Te spectra at energies higher than those of the above-reported lines. They have been attributed to phonon-assisted donor transitions involving the emission of A/Sb TO(T) and LO(T) phonons at 323 and 344 cm-1, respectively [4]. 

The selection and polarization rules for the np donor transitions from the Is (Ai) state in germanium for a stress along <111> are given in Fig. 8.6. Here, due the different valley group symmetry and stress orientation, the selection rules differ from those in silicon and one more component is observed for E//F. 

Table 8.13. Splitting A1C of the Zeeman components of the Is (Ai) —> rip i i donor transitions in silicon in units of 2 //, i > I i/mi as a function of the orientation of the magnetic field B with respect to the valleys (D doublet, S singlet). The orientations of the pair of valleys are those of Fig. 8.1. Y (yes) and N (no) correspond to the observation conditions resulting from polarization, k is the propagation vector of the radiation. The number of components for each polarization is given in the last line for each orientation of B...

The oscillator strength, fD, and the radiative lifetime, rf, of the donor transition are related by [10]... 

Many methods to destroy these confounds are available including incineration, wet air oxidation, catalytic dehydrochlorination, reaction widi superoxide, photolysis in the presence of hydrogm donors, transition metal-promoted reductive dechlorinations using sodium borohydride or alkoxyborohydrides, electrolytic reductions, hydrogenolyses, " iron-pranoted dechlorination" and thermolysis over solid bases such as CaO/Ca(OH)2. All diese methods have drawback, especially when the toxic pollutants are already distributed in the soil, sludges, ground or surface waters, etc. 

We now perform an averaging over all possible orientations of the donor transition dipole moment to get... 

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