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We develop a new set of models for intermediate-metallicity single stellarpopulations in the blue/optical region and use those models to determine thespectroscopic age of 47 Tuc. The models are based on a moderatelyhigh-resolution (1.8 A FWHM) empirical spectral library, state-of-the-arttheoretical isochrones from M. Salaris and the most recent set from the Padovagroup, and new semi-empirical calibrations between fundamental stellarparameters and observables. We highlight the importance of correctly modelingthe luminosity function (LF) of the cluster at the level of the giant branch,in order to achieve a good reproduction of the integrated spectrum; agreementbetween the spectroscopic age and the age based on the cluster'scolor-magnitude diagram (CMD) is achieved only if the observed LF is usedrather than the theoretical ones, which either do not include AGB stars(Salaris) or underpredict the total number counts of bright giants in thecluster by a factor of two(Padova). After all corrections are made, the CMD andthe spectroscopic ages (from Hgamma and Hbeta) are in close agreement: 11--12Gyrs for Salaris isochrones and about 13 Gyrs for Padova. The differencebetween the model ages is due to the inclusion of atomic diffusion in theSalaris models. Previously older spectroscopic ages were due to theunderestimate of the number of red giants and/or the use of isochrones thatneglected the effects of He-diffusion and alpha-enhancement. A similarunderestimate in the bright giant LF, if it exists in current super-solarmetallicity models, would cause spectroscopic ages of elliptical galaxiesinferred from such models to be too high by approximately 30%.Comment: 36 pages, including 13 Figures and 1 Table. Final, refereed version,  to appear in the December/2002 issue of ApJ. The new version is considerably  improved, by the inclusion of a whole new analysis based on the Padova  isochrone

Population Synthesis in the Blue. II. The Spectroscopic Age of 47 Tucanae