  Laser-ion acceleration with ultra-short pulse, PW-class lasers is dominated
by non-thermal, intra-pulse plasma dynamics. The presence of multiple ion
species or multiple charge states in targets leads to characteristic
modulations and even mono-energetic features, depending on the choice of target
material. As spectral signatures of generated ion beams are frequently used to
characterize underlying acceleration mechanisms, thermal, multi-fluid
descriptions require a revision for predictive capabilities and control in
next-generation particle beam sources. We present an analytical model with
explicit inter-species interactions, supported by extensive ab initio
simulations. This enables us to derive important ensemble properties from the
spectral distribution resulting from those multi-species effects for arbitrary
mixtures. We further propose a potential experimental implementation with a
novel cryogenic target, delivering jets with variable mixtures of hydrogen and
deuterium. Free from contaminants and without strong influence of hardly
controllable processes such as ionization dynamics, this would allow a
systematic realization of our predictions for the multi-species effect.
