2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/46805A QCD based calculation of the photon spectrum in semi-inclusive $η_Q$ decays is performed. The method applied is an effective theory based on a 1/m_Q expansion of QCD.Latex, 15 pages, 2 postscript figures included, uses epsf. The complete paper, including figures, is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints/High Energy Physics - Phenomenologytext