  Strong shocks propagating into a partially ionized medium are often
associated with optical Balmer lines. This emission is due to impact excitation
of neutral hydrogen by hot protons and electrons in the shocked gas. The
structure of such Balmer-dominated shocks has been computed in a previous paper
(Blasi et al. 2012), where the distribution function of neutral particles was
derived from the appropriate Boltzmann equation including coupling with ions
and electrons through charge exchange and ionization. This calculation showed
how the presence of neutrals can significantly modify the shock structure
through the formation of a "neutral-induced" precursor ahead of the shock. Here
we follow up on our previous work and investigate the properties of the
resulting Balmer emission, with the aim of using the observed radiation as a
diagnostic tool for shock parameters. Our main focus is on Supernova Remnant
shocks, and we find that, for typical parameters, the H{\alpha} emission
typically has a three-component spectral profile, where: 1) a narrow component
originates from upstream cold hydrogen atoms, 2) a broad component comes from
hydrogen atoms that have undergone charge exchange with shocked protons
downstream of the shock, and 3) an intermediate component is due to hydrogen
atoms that have undergone charge exchange with warm protons in the
neutral-induced precursor. The width of the intermediate line reflects the
temperature in the precursor, while the width of the narrow one is left
unaltered by the precursor. In addition, we show that the profiles of both the
intermediate and broad components generally depart from a thermal distribution.
Finally, we show that a significant amount of Balmer emission can be produced
in the precursor region if efficient electron heating takes place.
