Engineering topics

Strazzulla, G.

Publications and source records attributed to Strazzulla, G..

4 records

NASA NTRS2000

R-O-C(triple bond)N species produced by ion irradiation of ice mixtures: comparison with astronomical observations

We have investigated the effects induced by ion bombardment of mixtures containing nitrogen-bearing compounds at low temperatures. The results show the formation of a band at 2080 cm-1 in binary mixtures, NH3:CH4 and N2:CH4, which we attribute to HCN embedded in the organic residue formed by ion irradiation. In addition to this band, ternary mixtures containing an oxygen-bearing species (i.e., H2O) form a compound with a prominent absorption band at about 2165 cm-1 (4.62 microns). We ascribe this band to a nitrile compound containing O that is bonded to the organic residue. A detailed comparison of the laboratory results with astronomical data of the 4.62 microns absorption band in protostellar spectra shows good agreement in peak position and profile. Our experimental studies show that N2, which is a more likely interstellar ice component than NH3, can be the molecular progenitor of the carrier of the interstellar band. This is an alternative to the pathway by which UV photolysis of NH3-containing ices produces the 4.62 microns band and implies that ion bombardment may well play an important role in the evolution of interstellar ices. Here, we discuss the implications of our studies for the chemical route by which the carrier of the 4.62 microns band is formed in these laboratory experiments.

NASA Discipline Exobiology↗

NASA NTRS1992

Ion produced cometary organic crust

For several years many experimental results have been obtained on the chemical and physical changes induced by ion and electron irradiation of materials with a view to their Astrophysical relevance. Among the studied effects, one of particular interest is the formation of an organic refractory residue left over after ion irradiation and warming-up at room temperature. We call this residue IPHAC (ion produced hydrogenated amorphous carbon). Although 'in situ' infrared spectroscopy points out the formation of new molecular species during bombardment at low temperature, it is not clear if IPHAC is already formed or if its formation is triggered by temperature increase during warming-up of the irradiated target. Since Raman Spectroscopy is a technique particularly suitable for the analysis of carbonaceous materials, we have thought and build-up an experimental apparatus to obtain Raman Spectra of frozen hydrocarbons during ion irradiation. The present experimental results point out clearly to the formation of IPHAC already at low T and low energy deposition (approximately equal to a few eV/C-atom).

Baratta, G. Antonio↗

NASA NTRS1991

Primordial comet mantle - Irradiation production of a stable, organic crust

The thickness and survivability of a cosmic ray-generated primordial comet refractory mantle, or 'crust', are presently predicted by laboratory data and corrected estimates of cosmic ray dose to be capable of surviving a new comet's entry into the inner solar system over numerous revolutions. It is suggested that, since this mantle may be as much as several meters deep, the probe apparatus of the projected CRAF and Rosetta spacecraft will have to be extended in order to reach the desired, unprocessed cometary material. As things stand, there is a high probability that these missions will sample cometary matter than has been heavily irradiated and reprocessed in the Oort cloud.

Strazzulla, G.↗

NASA NTRS1991

Irradiation effects on comets and cometary debris

Experimental results obtained over the past 10 years on the chemical and physical changes induced by ion and electron irradiation of materials relevant to comets are reviewed, and their physical interpretation and their relevance for cometary astrophysics are addressed. Four phases of the irradiation history are considered: the precometary phase, the accretion phase, the cometary phase, and the postcometary phase. The relevant applications of laboratory results are reviewed. The ability of ion irradiation of simple carbon-containing ices to produce complex refractory organic materials is discussed. In the Oort cloud, this process can occur several meters into the surface, so that the buildup of a stable organic crust may occur. Ion irradiation at various stages is compared with other models for the production of organics.

Strazzulla, G.↗