Molecular complexity of the O-rich pre-Planetary Nebula OH231.8

Envelopes around evolved stars are extraordinarily efficient factories of complex molecules and dust particles that will eventually enrichthe ISM. To date, most chemistry studies have focused on Crichenvelopes, expected to show the largest molecular variety andabundances. Recent observations suggest that Orich shells may be aschemically diverse as their Carbon counterparts, however, no seriousattempt has been made yet to perform a full frequency scan of suchobjects. We propose to carry out a line survey with HIFI of the wellknown, Orich prePN OH 231.8, which displays fast (>400 km/s),bipolar outflows and a molecular richness unparalleled amongst OrichAGB and postAGB stars. Results from our exploratory mm line surveywith the IRAM 30 m antenna of this object has led to the detection ofhundreds of lines from different species that clearly point tononequilibrium/shockinduced molecule formation processes in the fastflow. The HIFI could be potentially effective to reveal the dense andwarm regions near the centre, which is strongly affected by shocks.At its completion, this project will provide the sorely neededmolecular inventory and abundance measurements in Orich CSEs, which are required to obtain a better understanding of the intricate,nonequilibrium molecule formation processes in Orich environments.We will use our radiative transfer and chemistry models to reproducethe observed spectra and empirically derived abundances, respectively,and constrain the nebular physical and chemical conditions in theenvelope of OH231. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]