  We argue that the photon spectra in radiative decays of various heavy
quarkonium states provide important information on their nature. If two of
these states are in the strong coupling regime, we are able to produce a
parameter-free model independent formula, which holds at next-to-leading order
and includes both direct and fragmentation contributions. When the formula is
checked against recent CLEO data it favors Upsilon (2S) and Upsilon (3S) in the
strong coupling regime and disfavors Upsilon (1S) in it.
