Herschel-HIFI observations of high-J lines (up to
Ju = 10) of 12CO, 13CO and
C18O are presented toward three deeply embedded low-mass protostars in NGC
1333. The observations show several energetic components including shocked and quiescent
gas. Radiative transfer models are used to quantify the C18O envelope abundance
which require a jump in the abundance at an evaporation temperature,
Tev ~ 25 K, providing new direct evidence of a CO
ice evaporation zone around protostars. The abundance in the outermost part of the
envelope, X0, is within the canonical value of
2 × 10-4; however the inner abundance, Xin, is
found around a factor of 3–5 lower than X0.