  We present new accurate abundances for five neutron-capture (Y, La, Ce, Nd,
Eu) elements in 73 classical Cepheids located across the Galactic thin disk.
Individual abundances are based on high spectral resolution (R ~ 38,000) and
high signal-to-noise ratio (S/N ~ 50-300) spectra collected with UVES at ESO
VLT for the DIONYSOS project. Taking account for similar Cepheid abundances
provided either by our group (111 stars) or available in the literature, we end
up with a sample of 435 Cepheids covering a broad range in iron abundances
(-1.6 < [Fe/H] < 0.6). We found, using homogeneous individual distances and
abundance scales, well defined gradients for the above elements. However, the
slope of the light s-process element (Y) is at least a factor of two steeper
than the slopes of heavy s- (La, Ce, Nd) and r- (Eu) process elements. The s to
r abundance ratio ([La/Eu]) of Cepheids shows a well defined anticorrelation
with of both Eu and Fe. On the other hand, Galactic field stars attain an
almost constant value and only when they approach solar iron abundance display
a mild enhancement in La. The [Y/Eu] ratio shows a mild evidence of a
correlation with Eu and, in particular, with iron abundance for field Galactic
stars. We also investigated the s-process index - [hs/ls] - and we found a well
defined anticorrelation, as expected, between [La/Y] and iron abundance.
Moreover, we found a strong correlation between [La/Y] and [La/Fe] and, in
particular, a clear separation between Galactic and Sagittarius red giants.
Finally, the comparison between predictions for low-mass asymptotic giant
branch stars and the observed [La/Y] ratio indicate a very good agreement over
the entire metallicity range covered by Cepheids. However, the observed spread,
at fixed iron content, is larger than predicted by current models.
