Theoretical computations on the efficiency of acetaldehyde formation on interstellar icy grains

Interstellar grains are known to be important actors in the formation of interstellar molecules such as H$_2$, water, ammonia, and methanol. It has been suggested that so-called complex organic (iCOMs) also formed on grain icy surfaces by combination radicals via reactions assumed have an efficiency equal unity. In this work, we aim investigate robustness or weakness assumption considering case acetaldehyde (CH$_3$CHO) a starting study case. literature, it postulated is HCO CH$_3$. Here report new theoretical computations its formation. To end, coupled quantum chemical calculations energetics kinetics reaction CH$_3$ + HCO, which can lead CH$_3$CHO CO CH$_4$. Specifically, combined computed with Rice-Ramsperger-Kassel-Marcus (RRKM) theory (tunneling included) method diffusion desorption competitive channels. We provide results our format used astrochemical models facilitate their exploitation. Our indicate function temperature and, more importantly, over binding energy ratio $f$ radical. If $\geq$0.4, unity range where occur, namely between 12 30 K. However, if smaller, dramatically crashes: $f$=0.3, at most 0.01. addition, always competition