GASEOUS REFRACTORY-ELEMENT MOLECULES IN IRC10216

The list of detected refractory-element (RE) species in IRC10216 is no w large enough to try to assess their chemistry, and the fraction of e ach that escapes in gas phase to the ISM. The former may tell us how g rains are formed, the latter whether mass-loss from evolved stars is i mportant in determining interstellar elemental depletions as distinct from accretion processes in the ISM. We expect that much of the Si che mistry is now understood and about 25% of Si escapes as a gas. Other R Es are less well understood but most should be more volatile than Si. For many of the REs, O-rich CSEs should behave similarly to C-rich one s.