  Knockout reactions with heavy ion targets in inverse kinematics, as well as
"quasi-free" (p,2p) and (p,pn) reactions are useful tools for nuclear
spectroscopy. We report calculations on \textit{ab-initio} many-body
wavefunctions based on the no-core shell model to study the nucleon removal
reactions in light nuclei, including beryllium, carbon, and oxygen isotopic
chains, and explore the importance of using an \textit{ab-initio} method. Our
study helps clarifying how the extraction of spectroscopic factors from the
experiments depend on the details of the many-body wavefunctions being probed.
We show that recent advances with the ab-initio method can provide more
insights on the spectroscopy information extracted from experiments.
