Abstract:
   Poincare Fluorescence, the process accompanied by de-excitation of
a  molecule in the high internal energy state, had been predicted and
examined in the field of physical chemistry and atomic physics in the
late 70fs. However since then, it has been almost forgotten because of
the ambiguity of the experimental confirmation. In 1988, this process
was re-discovered or proposed by a theorist from a viewpoint of
astrophysics. Recently, with a technological progress of ion traps or
ion storage rings, several groups have reported that this process indeed
exists and takes place, by experimentally tracing the de-excitation
process of an isolated single molecular ion in vacuum.
   Especially, we very recently have succeeded in direct observation of
Poincare fluorescence.
   The composition of interstellar clouds is heavily influenced by the
fate of the molecules after excitation by light absorption or after the
collision. In the dilute interstellar space, emission of radiation is
the only means by which the molecules can stabilize after excitation
above the decomposition threshold. From such a context, the existence of
this fluorescence process is important for astrochemistry.
   In this talk, starting with comprehensive introduction of Poincare
fluorescence following the inverse internal conversion, I will explain
why it has not been found in spite that its existence is naturally
expected, together with its significance in astrochemistry.