We report on an observation of the luminescence spectrum of mass-selected CuAg in an argon matrix. Although no Raman spectrum is obtained, an emission progression up to v" = 5 is observed, corresponding to the A0(+)-X(1)Sigma(+) transition observed in the gas phase. The origin of the transition is determined to be 20 262 (10) cm(-1). We obtain a value of omega"(e) = 223.8(4.9) cm(-1), which is consistent with the gas-phase observations. e (C) 2003 Elsevier Science B.V. All rights reserved.