Energy levels metastable excited

Figure 5.61 summarizes the temperature behavior of decay time r and quantum efficiency xj of the blue luminescence from benitoite in the forms ln(r) and ln(q) as a function of reciprocal temperature 1/T. Figure 5.62.a demonstrates a suitable energy levels scheme. After excitation the metastable level 1 is populated due to nonradiative fast transition from excited level. Between levels 1 and 2 the equilibrium population is established due to nonradiative transition. The relative quantum yield of the blue emission may be described by simple Arrhenius equation ... 

For the 4f7 configuration of Eu2+, the host sensitive energy levels of the 4f65d states are not far from the metastable 4f7 6P7/2 multiplet near 27 000 cm-1. The strength of crystal field interaction determines whether the lowest 4f65d state is above or below the excited 4f7 multiplet, which is insensitive to host lattice. Because there is no 4f state below 6P7/2, strong blue luminescence arises from the parity allowed 4f55d-4f7 transition. The intensity of the... 

Trivalent neodymium absorbs strongly in broad bands in the green, red and near infra-red with reasonable coincidence in the output of a xenon flash lamp. Nearly all the electrons excited into the pump bands revert to the metastable upper level 4F3/2 through non-radiative decay which has a lifetime of 230 ps. Radiative transition then occurs to a set of lower energy levels 4I)5/2,4Ii3/2,4I 1/2,4l9/2- All these levels are multiplets and the lowest of 4l9/2 is... 

The most probable photochemical primary process of the polymerization reaction is shown in the energy level diagramm of Fig. 24. In the photoinitiation reaction an excited adjacent monomer molecule M is added to the reaction center, best represented by the metastable triplet DRi monomer molecule. Owing to the spin conservation rules, we conclude that an excited triplet dimer- diradical DR2 is formed in the chemical reaction. We may, therefore, formulate the reaction as follows ... 

To obtain stimulated emission between two energy levels, a population inversion is necessary. This is usually achieved by excitation into a third level or levels which rapidly and efficiently transfer energy to a metastable upper laser level. 

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