F. Baas

Photochemical reactions in interstellar grains photolysis of co, NH3, and H2O

A simulation of the organic layer accreted onto interstellar dust particles was prepared by slow deposition of a CO:NH3:H2O gas mixture on an Al block at 10K, with concomitant irradiation with vacuum UV. The residues were analyzed by GC-MS, HPLC, and near IR; a reaction pathway leading from NH3 to complex alcohol, fatty acid, and amide products in 27 stages is postulated. The astronomical relevance and significance of the observations are discussed.

Infrared spectrum of the complex of formaldehyde with carbon dioxide in argon and nitrogen matrices

The complex of formaldehyde with carbon dioxide has been studied by infrared spectroscopy in argon and nitrogen matrices. The shifts relative to the free species show that the complex is weak and similar in argon and nitrogen. The results give evidence for T-shaped complexes, which are isolated in several configurations. Some evidence is also presented which indicates that, in addition to the two well-known sites in argon, carbon dioxide can be trapped in a third site.

Identification of the emission feature near 3.5 microns in the pre-main-sequence star HD 97048

The spectrum of HD 97048 has been measured with a resolving power of 450 between 3.37 and 3.64 ..mu..m. The prominent feature near 3.5 ..mu..m, discovered by Blades and Whittet, is well resolved, with a peak at 3.53 ..mu..m and a wing extending to shorter wavelength. The weaker feature near 3.4 ..mu..m is found to peak at 3.43 ..mu..m, in contrast to the 3.40 ..mu..m feature seen in other astronomical objects. The observed spectrum strongly resembles labaoratory spectra of mixtures of monomeric and dimeric formaldehyde embedded in low-temperature solids. Of various possible excitation mechanisms, ultraviolet pumped infrared fluorescence of formaldehyde in interstellar grains provides the best explanation for the observed spectrum of HD 97048.

Molecular Origin of the 216 NM Interstellar Hump

Vacuum ultraviolet photochemical experiments have been performed in an argon matrix, at low temperature (− 12 K). It appears that starting from a variety of simple organic molecules photo-products are formed which nearly always show strong light absorption in the 200- 235 nm range. Infrared and ultraviolet spectra indicate that the absorbing species are polyacetylene and cyano-polyacetylene type molecules. Such molecules are found in space. The polyacetylenes and cyano-polyacetylenes have extremely strong light absorption bands in the ultraviolet; in a matrix the shift in band position is quite large. It is suggested that such molecules on grains could give rise to the 216 nm interstellar extinction hump.

Chemiluminescence of N2, NH, and O2 in argon matrices

Abstract The chemiluminescence spectra from O 2 NO, N 2 and NH have been obtained, during warm-up of VUV photolyzed mixtures of argon containing small amounts of H 2 O and/or NH 3 . The spectra can be explained by recombination reactions between the trapped (ground state) atoms N( 4 S) and O( 3 P), and in the case of the observed NO β system, also by the excited N( 2 D) atoms. The presence of N( 2 D) atoms during sample warmup is further evidenced by the observed. N( 2 D) → N( 4 S) transition. Recently chemiluminescence spectra have also been obtained from photolyzed Ar/CH 4 /H 2 O mixtures. Among the many spectral features observed are the Cameron bands of CO.

High Velocity H2 Line Emission in the NGC 2071 Region

The line profile of the v=1→0 S(1) line of H2 in NGC 2071 is ~100 km s-1 wide (FWZI), and asymmetric; it resembles S(1) profiles seen toward Orion KL. The NGC 2071 region represents the second detection of high velocity H2 emission in a region showing signs of ongoing star formation.