The following document lists the file abstract/DNEUFELD_HALOGENS.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
=============================================================================== ==> This proposal requests an upgrade from Priority 3 for DNEUFELD.HHALIDES (Please note that the scientific justification and proposed observing programme have been modified in response to developments since the pre-launch call.) =============================================================================== We propose to search for far-infrared transitions of interstellar hydrogen chloride and hydrogen fluoride. We expect the proposed observations to serve as a valuable probe of the chemistry of halogen-bearing interstellar molecules. For hydrogen chloride, we will search for the far-infrared J=3-2 rotational transition in two sources: Sagittarius B2, in which the submillimeter J=1-0 line of HCl has recently been detected in absorption using the KAO; and the Orion Molecular Cloud 1 (OMC-1), in which the J=1-0 line has been detected in emission and has recently been mapped. Based upon theoretical models for the excitation of HCl J=1-0 in these sources, we expect the J=3-2 transitions to be easily detectable with ISO. Measurements of the higher-lying J=3-2 line will serve to constrain the excitation conditions in the source and will allow the HCl abundance to be determined more reliably. For hydrogen fluoride, we will search for the J=2-1 rotational transition in the same two sources. A very recent ground-based spectral line survey of the Orion region has led to the detection of a single line that has been tentatively identified as the J=1-0 transition of deuterium fluoride (DF); unfortunately, the analogous transition of HF cannot be detected from the ground because of atmospheric absorption, so space-based observations will be needed to search for hydrogen fluoride. If the identification of DF in Orion is correct, then the depletion of fluorine must be small and HF must be a major reservoir of gas-phase fluorine. A detection of HF J=2-1 would mean the first unequivocal detection of a fluorine-bearing interstellar molecule.