| Abstract
| - Herschel-HIFI observations of high- J lines (up to Ju = 10) of 12CO, 13CO and C 18O 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 C 18O 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.
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