Europium intraconfigurational transition intensities and emission quantum yields

Europium intraconfigurational transition intensities and emission quantum yields 

The narrow absorption and emission bands of rare-earth 0-diketonates in the visible, near ultra-violet and near infra-red is attributed to 4f-4f transitions. These transitions are electric dipole forbidden to first order, but are allowed by the electric quadrupole, vibronic, magnetic dipole and forced electric dipole mechanisms. The magnetic dipole character of the Dq F transition of the Eu + ion was demonstrated in 1939 by 

Deutschbein . Most of the intraconfigurational 4f transitions in the RE ions, however, cannot be accounted for by the magnetic dipole mechanism, not only because the predicted oscillator strengths are in general smaller than 10 , but also due to the restrictive selection rules on the total angular momentum 7, A7 =0, 1 (0 0 excluded), as far as 7 is considered to be a good quantum number. 

From all the Aqj, it is possible to calculate the total spontaneous emission for the emitting Dq level, in this case given by Arad = H Aoy = Aqo + Aqi + A02 + A03 + A04. 

Moreover, it is possible to determine the emission efficiency r] = Arad/ nrad of the emitting level, where the total decay rate is Atot = 1/r = Arad + nrad. and where the non-radiative component A rad depends on the vibronic couphng between the Eu ion and its chemical environment and r is the lifetime of the Do emitting level. It may be determined from lifetime measurements and the experimentally determined radiative component Arad- The hydrated Eu + S-diketonates tend to present lower values of emission quantum efficiencies, and emission quantum yields, in agreement with the well known effect of luminescence quenching due to the vibrational modes of the water molecule. 

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