The characteristic intraconfigurational 4f(11) fluorescence of the tri
valent erbium I-4(13/2) --> I-4(15/2) transition has been observed in
endohedral Er-2@C-82. The fluorescence is weak and the lifetime is ver
y short because of quenching by energy transfer to the carbon cage. Hy
drogenating the carbon cage changes the spectrum and markedly increase
s the fluorescence.