  The universal aspects of two-body collisions in the presence of a harmonic
confinement are investigated for both bosons and fermions. The main focus of
this study are the confinement-induced resonances (CIR) which are attributed to
different angular momentum states $\ell$ and we explicitly show that in
alkaline collisions only four universal $\ell$-wave CIRs emerge. Going beyond
the single mode regime the energy dependence of $\ell$-wave CIRs is studied. In
particular we show that all the $\ell$-wave CIRs may emerge even when the
underlying two-body potential cannot support any bound state. We observe that
the intricate dependence on the energy yields resonant features where the
colliding system within the confining potential experiences an effective
free-space scattering. Our analysis is done within the framework of the
generalized $K$-matrix theory and the relevant analytical calculations are in
very good agreement with the corresponding ab initio numerical scattering
simulations.
