A KEY SPECTROSCOPIC STUDY OF CRL618 SHOCKED CHEMISTRY IN POST-AGB EVOLUTION

> in this proposal, more observing time is requested for irc_spec and neri_1 crl618 is the brightest crich ppn star. it has a very rich chemistry characterized by the large variety of molecular species formed in the different regions of its circumstellar envelope and in the innermost shocked regions of its cse. we propose to perform a full spectral survey of this object between 2.38 and 196.7 um using the sws and lws instruments. the sws full resolution grating sweep between 2.38 and 45 um will allow us to determine the molecular content of all molecular species through their stretching or bending vibrational bands. the sws grating mode and fabryperot observations will probe the high velocity gas in this object which is in the evolutionary track from the lateagb to the young pn stage. the proposed observations are expected to shed light on the chemical abundances and excitation conditions in the high velocity winds (hvws) and will provide us with new information that will permit us to refine current knowledge on the evolutionary appearance of hvws. finally, we would like to perform a fast lws fp scan of crl618 between 43 and 196.7 um. the signal to noise ratio will be large enough to detect strong absorption or emission lines of heavy molecules or fine structure atomic lines. key molecules like c3, c4, c5, c6, c4h, c5h, c6h, c4h2, c6h2, .., have their lowlying bending levels in the lws frequency coverage. this spectral scan will permit to identify these species, study their role in the growth of carbon chains and to characterize their spectral constants. in order to fully characterize this object we would like to perfom an isocamcvf from 5 to 18 um. the dust emission, together with the molecular emission, will allow a detailed study of this remarkable object. after irc+10216, crl618 has the richest mo trunca [truncated!, Please see actual data for full text]