4f energy

Stabilization (AE ) and Destabilization (A 4f) Energies (in kcal/mol) Obtained for Furan, Pyrrole, Thiophene, and Benzene at the STO-3G (STO-3G for Thiophene) Computational Level [88JST(163)173]... 

We have seen earlier that Eu3+ possess two resonance levels, Do mid 5Z>i, from which fluorescence transitions to the J manifold of 1F takes place. The 5Do - 7Fo transition is strictly forbidden for regular octahedral symmetry but is observed in some complexes due to the lack of centro-symmetry. The intensity of the fluorescence transition is not directly dependent only on the amount of T 4f energy transfer, but mainly on the transition probabilities from a particular resonance level to the various J manifolds. However, the transition probabilities are sensitive functions depending on the ligand. A schematic representation of the... 

The change of the X component allows for a change of the valence electron concentration and one can thus modify the separation between the Fermi energy and the 4f energy levels. The ternary compounds CesPd24X have significantly different properties than binary CePd3 (see Section 5.5). 

Fig. 2. Complete 4f" energy level diagram for all RE3+ ions obtained by semiempirical calculations.

Fig. 15. (a) Schematic Er excitation model, showing the electronic band structure of Si nanocrystall-doped Si02 and the Er 4f energy levels. An optically generated exciton (dotted line) confined in the nanocrystal can recombine and excite Er3+. (b) Schematic representation of SiC>2 containing Er (crosses) and nanocrystals (circles). The nanocrystals that couple to Er (filled circles) show no exciton luminescence (redraw after (Kik and Polman, 2001)). 

Another characteristic of rare earth ions (except for Ce + and Yb +) in absorption spectra are their linear-like behavior. This comes from f-f transitions where 4f electrons exchange between different 4f energy levels. However, no f-f transition is allowed for Ce +(4f ) or Yb + (4f ). The broad absorption bands observed originates from configuration transitions, for example 4f" to 4f" 5d ... 

Facile ligand modification To improve the chemical and physical properties of the emitting materials, such as suitability for vapor phase deposition, solubility, stability or carrier transporting properties, modification of the ligands is necessary. Since the 4f shells of trivalent lanthanide ions are well shielded by the filled 5s and 5p orbitals, the 4f energy levels are only weakly perturbed by the environment outside of the lanthanide ions. Thus, the modification does not result in much shift in the emission wavelength. 

First, let us set up a J-matrix to calculate the 4f energy levels in L-S coupling, using the Hamiltonians of 6.8.10. Although we have already said that this method does not work, we stfil need to examine the general method of calculation. WE FIRST SET UP A SERIES OF MATRICES, using the Hartree-Fdk methods already developed for Quantum Mechanics. The next step is to then reduce them in terms of Slater determinants, namely-... 

Transition between 4f 4f energy levels are strictly forbidden, according to Hund s Rules, and are classified as quadrupole (qq) transitions. Their intensities ought to be I 10, but experimentally, I s 1.0, i.e.-intensities rivaling dd- transitions. 

Let us focus on the photophysical intermetallic communication 2 resulting from intramolecular 4f —>4f energy transfer and whose global efficiency is given in Eq. (75). 

FIGURE 122 Schematic representation of a nd-to-4f energy transfer (left) and of a 4f-to-nd transfer (right) along with the definition of the rate constants. 

Peijzel PS, Meijerink A, Wegh RT, Reid MF, Burdick GW (2005) A complete 4f" energy level diagram for all trivalent lanthanide ions. J Solid State Chem 178(2) 448-453... 

Gruber JB, Hills ME, Allik TH, Jayasankar CK, Quagliano JR, Richardson FS (1990) Comparative analysis of Nd (4f ) energy levels in four garnet hosts. Phys Rev B 41 7999-8012... 

Due to compression, pressure causes an increase of 4f energy with respect to the band states, and the ETE that diminishes energy of the anomalous luminescence and stabilize ETE state. 

---