  We investigate the excitation properties of finite utracold bosonic systems
in a one-dimensional harmonic trap with a time-dependent interaction strength.
The driving of the interatomic coupling induces excitations of the relative
motion exclusively with specific and controllable contributions of momentarily
excited many-body states. Mechanisms for selective excitation to few-body
analogues of collective modes and acceleration occur in the vicinity of
resonances. We study via the few-body spectrum and a Floquet analysis the
excitation mechanisms, and the corresponding impact of the driving frequency
and strength as well as the initial correlation of the bosonic state. The
fundamental case of two atoms is analyzed in detail and forms a key ingredient
for the bottom-up understanding of cases with higher atom numbers, thereby
examining finite-size corrections to macroscopic collective modes of
oscillation.
