The ISO/LWS spectrum of the EGG nebula, AFGL 2688.

We present an ISO Long Wavelength Spectrometer (LWS) grating spectrum of the carbon-rich proto-planetary nebula AFGL 2688 between 43 and 194μm. The far-infrared spectrum of AFGL 2688 is dominated by strong rotational transitions of CO which are detected from J=14-13 up to J=23-22. The atomic fine structure lines [O I] and [C II] are not detected. This is consistent with the cool central star of AFGL 2688 not having yet photodissociated the molecular gas ejected during the AGB phase. The far-infrared CO emission in AFGL 2688 appears to originate in shocked dense gas at a temperature of ~400K.