  We complement our study of alpha/Fe enhanced stellar population models of
Lick absorption indices (Thomas et al. 2003) by comparing two sets of alpha/Fe
enhanced models. In both models the impact on Lick indices due to alpha/Fe
enhancement is accounted for through a modification of the stellar absorption
line-strengths using the response functions of Tripicco & Bell (1995). One set
of models, however, uses solar-scaled, the other alpha/Fe enhanced stellar
evolutionary tracks. Since the alpha/Fe enhanced tracks are hotter than the
solar-scaled ones (Salasnich et al. 2000), the correspondent stellar population
models have slightly weaker metallic indices (i.e. Mgb, <Fe> etc.) and stronger
Balmer line indices (Hbeta) (Maraston et al 2003). Here we explore
quantitatively the impact of this effect on the alpha/Fe ratios, metallicities
and ages that are derived for elliptical galaxies. We find that the modest
decrease of the metallic indices Mgb and <Fe> balance each other, such that
fully consistent alpha/Fe ratios are derived for stellar systems using alpha/Fe
enhanced models with either solar-scaled or alpha/Fe enhanced stellar tracks.
The decrease of the metallic indices and the increase of Hbeta conspire in a
way that also consistent metallicities are obtained. The derived ages, instead,
are significantly different. The inclusion of alpha/Fe enhanced stellar tracks
leads to the derivation of ages as high as 30 Gyr for elliptical galaxies. For
the same objects, ages not older than 15 Gyr are obtained, if alpha/Fe enhanced
models using solar-scaled tracks are adopted. This may indicate that current
stellar evolutionary models overestimate the bluing of stellar evolutionary
tracks due to alpha/Fe enhanced chemical mixtures at super-solar metallicities.
