Quark content of neutral mesons

Radiative transitions involving neutral mesons with J/sup P/ = 0/sup -/ (eta,eta',iota(1440)) and 2/sup +/ (f,f',theta(1640)) are used to provide information on the light-quark content of these mesons, and to test predictions of models in which these states are quarkonium-gluonium mixtures. Some suggested observations include (l) phi..-->..eta'..gamma.., predicted to have a branching ratio of 7 x 10/sup -5/ in the standard quarkonium picture of eta', (2) f'..--> gamma gamma.., predicted to have a partial width > or approx. =200 eV if f' = ss-bar but very sensitive to possible destructive interference from small nonstrange-quark admixtures, and (3) iota(1440)..--> gamma gamma.. and theta(1640)..--> gamma gamma.., which will be easily detectable unless these states are almost totally free of quarkonium admixtures.