Temperature dependence of the fluorescence quantum yield and decay time of several rare-earth chelates have been studied in an attempt to understand the quenching mechanisms in these compounds. It is observed that the quenching in either the ligand or the ion is reduced by lowering the amplitude of molecular vibrations. This indicates that a major part of the fluorescence quenching in rare-earth chelates occurs due to coupling of the electronic states to the environment through molecular vibrations. The results of the present measurement also indicate that the shielded 4f orbitals of the rare-earth atoms become more impervious to quenching when they are incorporated into a chelate. Importance of these results in connection with liquid laser research is discussed.

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Einstein is considered by many as the father of quantum physics in some sense. Yet there is an unshakable view that he was wrong on quantum physics. Although it may be a subject of considerable debate, the core of his allegedly wrong demurral was the insistence on finding an objective reality underlying the manifestly bizarre behavior of quantum objects. The uncanny wave-particle duality of a quantum particle is a prime example. In view of the latest developments, particularly in quantum field theory, Einstein's objections are substantially corroborated. Careful investigation suggests that a travelling quantum particle is a holistic wave packet consisting of an assemblage of irregular disturbances in quantum fields. It acts as a particle because only the totality of all the disturbances in the wave packet yields the energy momentum with the mass of a particle, along with its other conserved quantities such as charge and spin. Thus the wave function representing a particle is not just a fictitious mathematical construct but embodies a reality of nature as asserted by Einstein.

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Intermolecular triplet-triplet energy transfer between aromatic carbonyls and aromatic hydrocarbons as donors and rare earth chelates as acceptors is demonstrated. This is accomplished by observing the phosphorescence from the triplet level of gadolinium chelate, as well as the intramolecularly sensitized emission of the Eu3+ ion in europium hexafluoroacetylacetonate. The transfer is shown to be diffusion controlled. The possibility of the transfer taking place via actual chemical reaction is discussed, but evidence indicates it to be highly improbable for the chelate-benzophenone system. The transfer from the benzophenone triplet level to the chelate triplet level is not found to be more efficient than that between benzophenone and naphthalene. This indicates that the heavy ion has little effect on the transfer probability. At concentrations of ~10~3 mole/1. the transfer between the ketone and the europium chelate triplet levels is found to be more efficient than the transfer between ketone and the bare Eu+3 ion. At higher concentrations, however, a rather efficient transfer of energy from the ketone to the ion is observed. Application of the last class of material for laser purposes is discussed. (1) (a) Work supported in part by Rome Air Development Center, Rome, N. Y., under Contract AF 30(602)-3440; (b) consultant to Electro-Optical Systems, Inc.; (c) contribution No. 1738.(2) D. L.

Time-resolved fluorescence spectra of several europium chelates have been measured using the stroboscopic time-resolution technique. For each of the β-diketone chelates, where the ligand triplet levels are in general above the 5D1 level of Eu3+, the spectra provide evidence that the Eu3+5D0 state is populated by nonradiative energy transfer from the higher-lying 5D1 state. The relaxation time for energy decay from the 5D1 state is measured both in the microcrystals and in solution to be of the order of a few microseconds. Since this is shorter than the corresponding relaxation time of Eu3+ in systems where there are no vibrational frequencies near 1760 cm−1, the 5D1—5D0 energy separation, it is suggested that the ligand[Complex chemical formula]stretching vibrations and the bending vibration of coordinated water molecules make important contributions to the relaxation process. On the other hand, complete nonradiative degradation to the molecular environment from the 5D0 and the 5D1 energy levels appears to be more strongly influenced by higher-energy molecular vibrations such as the C–H and O–H stretches. Variations with temperature in the relaxation time from the 5D1 energy level are mainly accounted for by the temperature dependence of the rate of energy degradation from the 5D1 level to the environment, and it is suggested that the [Complex chemical formula] relaxation process is temperature insensitive between 300° and 77°K. In general, the nonradiative energy-transfer processes in Eu3+ appear to be dominated by interactions with molecular vibrations, and to a smaller extent by crystal lattice modes, rather than by other possible relaxation mechanisms.

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