The effect of the kinematic factor on
vibronic spectra of europium compounds and Eu
3+-doped lanthanide compounds was examined experimentally. It was demonstrated that isotopic or quasi-isotopic substitution of the ions of the crystal lattice gi
ves rise not only to the changes of the
vibration frequencies but also to alteration of the
value of electron–phonon interaction. The latter displays in changing the relati
ve integral intensity of
vibronic sidebands of electronic transitions of Eu
3+ ion. Eu
3+ vibronic spectra of a number of pairs of natural and isotopically or quasi-isotopically substituted compounds: nitrates, halides, formates, acetates, oxalates,
β-diketonates, etc., were studied. In most cases the substitution of deuterium for hydrogen was applied. Decrease of the electron–phonon interaction with the increase of the isotopic mass depends on different structural characteristics. It was found that a factor of decreasing the relati
ve intensity of the
vibronic sideband of electronic transition of Eu
3+ ion lies within the range
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vert, similar"" border=0>1.2 and
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vert, similar"" border=0>7 for pairs of compounds under in
vestigation. The largest change of the intensity of
vibronic sidebands was obser
ved in a pair of formates Eu(HCOO)
3 and Eu(DCOO)
3 ha
ving the tridentate-bridging coordination of the formate anions and a three-dimensional frame structure. One should take into consideration both decreasing the
vibration frequencies and diminishing the
value of electron–phonon interaction at introduction of hea
vy isotope or quasi-isotope in the crystal lattice of lanthanide compounds to reduce the multiphonon quenching of luminescence.