Giuseppe Baratta - Academia.edu (original) (raw)
Papers by Giuseppe Baratta
Icarus, 1991
The thickness and survivability of a cosmic ray-generated primordial comet refractory mantle, or ... more 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
Topics in Applied Physics, 2006
Page 1. Vibrational Spectroscopy in Ion-Irradiated Carbon-Based Thin Films Giuseppe Compagnini1, ... more Page 1. Vibrational Spectroscopy in Ion-Irradiated Carbon-Based Thin Films Giuseppe Compagnini1, Orazio Puglisi1, Giuseppe A. Baratta2, and Giovanni Strazzulla2 ... 100, 505520 (2006) © Springer-Verlag Berlin Heidelberg 2006 Page 2. 506 Giuseppe Compagnini et al. ...
Radiation Physics and Chemistry, Mar 1, 2004
Polyphenylacetylene (PPA) thin films deposited on silicon substrates have been bombarded with a b... more Polyphenylacetylene (PPA) thin films deposited on silicon substrates have been bombarded with a beam of 30 keV of He + ions. The radiation damage of the film has been monitored by FT-IR spectroscopy at fluences between 0.8×10 19 and 1.1×10 20 ions/m 2. The spectral changes undergone by the PPA film have been interpreted in terms of chain scission with formation of acetylenic and saturated end groups, and in terms of crosslinking reaction and extensive radiolytic degradation. The expected PPA cyclization reaction, a reaction which transforms a linear polymer into a ladder polymer has not been observed, although polystyrene (PS) is able to give this kind of reaction under somewhat similar conditions to those adopted in the present work. The results have been discussed in an astrochemical context in relation to the infrared emission spectra of certain astrophysical object and molecules present in the interstellar medium.
Astron Astrophys, 2002
We have studied by infrared absorption spectroscopy the effects induced by fast ions (30 keV) and... more We have studied by infrared absorption spectroscopy the effects induced by fast ions (30 keV) and Lyman-alpha photons (10.2 eV) on some molecular ices at low temperature (10-20 K). It is well known that in both cases the physical and chemical properties of the ices are modified. However while the energy released by ions depends mainly on their energy and on the target species, the effects induced by photons also depend on the optical properties of the sample. Here we show that the effects of ion irradiation and UV photolysis are comparable on fresh ices (i.e. at low doses) but are increasingly different as processing is continued (i.e. at high doses).
Applied Physics Letters, Oct 12, 1992
Polarized Raman spectra have been performed in keV ion irradiated highly oriented pyrolytic graph... more Polarized Raman spectra have been performed in keV ion irradiated highly oriented pyrolytic graphite in order to investigate the disorder induced by energetic ions in the carbon matrix at room temperature. Early stages of ion irradiation (1012-1015 He+/cm2 3 keV) induce a high depolarization ratio of the 1360 cm-1 D line, leaving the 1580 cm-1 line almost unchanged. This was interpreted by an anisotropic damage induced in the highly oriented pyrolytic graphite structure by an ion collision cascade.
Journal of Geophysical Research Atmospheres, Nov 16, 2013
Infrared transmittance spectra of several volcanic ash samples positioned in the path of a IR bea... more Infrared transmittance spectra of several volcanic ash samples positioned in the path of a IR beam have been obtained. This technique is widely used in astronomy, in biological applications, in industrial and environmental fields. Nevertheless, in spite of its wide diffusion in several branch of science, up to now only few IR measurements on volcanic ash particles have been carried out in laboratory. In this work, infrared spectroscopy is used to investigate the spectral signature of volcanic ash particles emitted during the 21-24 July 2001 eruption at Mt. Etna, in Italy. A Bruker Equinox-55 FTIR interferometer operating in the range 1.43-16.67 µm is used to analyse the infrared transmittance of ash particles on KBr windows. For every collected spectrum, an image of the volcanic ash particles was recorded in the visible spectral range through the same microscope. These images are then analyzed by standard image analysis software in order to evaluate the main features of the particle...
Astronomy and Astrophysics
New experimental data demonstrating the transition from crystalline to amorphous water ice induce... more New experimental data demonstrating the transition from crystalline to amorphous water ice induced by keV ion-irradiation at temperatures between 10 and 80 K are presented. The procedure employed to monitor the structural changes is in situ IR spectroscopy. Results of some astrophysical applications show that such a process has to be considered when attempts to fit the astronomical spectra to those acquired in the laboratory are performed and especially when one attempts to deduce, from the shape of the observed ice band, information on the physical status, e.g., temperature history, of the responsible dust.
Some results, obtained from laboratory experiments of ion irradiation of ice mixtures containing ... more Some results, obtained from laboratory experiments of ion irradiation of ice mixtures containing H, C, N, and O bearing species are here summarized. They, in particular the formation of CN-bearing species, are relevant to the formation and evolution of complex organics on interstellar dust and small bodies in the external Solar System. Material incorporated into primitive Solar System bodies and delivered to the early Earth, may have contributed to the origin of life. The delivery of CN-bearing species seems to have been necessary because molecules containing the cyanogen bond are difficult to be produced in an environment that is not strongly reducing as that of the early Earth probably was. We report also on an ongoing research program concerning the interaction between refractory materials produced by ion irradiation of simple ices and biological materials (amino acids, proteins, celles), Perspective for possible future work is also given.
Ices, silicates, and carbonaceous materials have been observed in different astrophysical environ... more Ices, silicates, and carbonaceous materials have been observed in different astrophysical environments such as the interstellar medium, circumstellar regions, comets, and solid surfaces of Solar System objects. In space these materials suffer from processing caused by cosmic rays, photons and thermal annealing. Our knowledge of the effects of processing on the evolution of solids in different astrophysical environments in mainly based on laboratory experiments. The Laboratory of Experimental Astrophysics in Catania (Italy) is equipped to study the effects of processing on astrophysical relevant materials. Here we briefly describe the experimental set up and discuss some recent results.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014
In this paper we present the formation of carbon nanowires (polyynes and polycumulenes) in the so... more In this paper we present the formation of carbon nanowires (polyynes and polycumulenes) in the solid state by ion irradiation of frozen hydrocarbons (C 6 H 6 and C 2 H 2 ). Irradiations have been performed using H + ions in the 100's keV energy regime using fluences up to 5 Â 10 14 ions/cm 2 . Beyond the intrinsic significance of these results in the field of material science, this work has been motivated by the fact that ion beam irradiation of hydrocarbon ices is one of the most important process thought to happen in several extraterrestrial environments where many spectroscopic features of polyyne molecules have been identified.
The study of the evolution of organic matter subjected to space conditions, and more specifically... more The study of the evolution of organic matter subjected to space conditions, and more specifically to solar photons in the vacuum ultraviolet range (120-200 nm) has been undertaken in low Earth Orbit since the 90's, and implemented on various space platforms. The most recent exposure facilities are BIOPAN outside the Russian automatic capsules FOTON, and EXPOSE-E & -R (1&2) outside the International Space Station. They allow the photolysis of many different samples simultaneously, and provide us with valuable data about the formation and evolution of organic matter in the Solar System (meteorites, comets, Titan's atmosphere, the Martian surface...) and in the Interstellar Medium. They have been used by European teams in the recent past "Experimental astrochemistry: from ground-based to space-borne laboratories", University of Liège (Belgium), 2-3 July 2014, ed. M. De Becker 60 Bulletin de la Société Royale des Sciences de Liège, Vol. 84, 2014, p. 60 -73 (ORGANIC on BIOPAN V-FOTON M2 and UVolution on BIOPAN VI-FOTON M3, PROCESS on EXPOSE-E, AMINO and ORGANICS on EXPOSE-R), and a new EXPOSE set is currently exposed outside the ISS (PSS on EXPOSE-R2). These existing tools are very valuable; however, they have significant limitations that limit their capabilities and scientific return. One of the most critical issues for current studies is the lack of any in-situ analysis of the evolution of the samples as a function of time. Only two measurements are available for the experiment: one before and one after the exposure. A significant step forward has been achieved with the O/OREOS NASA nanosatellite and the OREOcube ESA project with onboard UV-visible measurements. However, for organic samples, following the evolution of the samples would be more informative and provide greater insight with infrared measurements, which display specific patterns characteristic of major organic functionalities in the mid-infrared range (4000-1000 cm −1 ).
Vis–NIR spectra of some Centaurs and Trans-Neptunian Objects (TNOs) indi-cate surfaces rich in H ... more Vis–NIR spectra of some Centaurs and Trans-Neptunian Objects (TNOs) indi-cate surfaces rich in H 2 O, N 2 , CO 2 , CH 4 e CH 3 OH. Cosmic ion irradiation is one of the processes driving the evolution of TNO surfaces. A main role is played by the chemistry induced by colliding ions; many molecular bonds are broken along the ion track, and this may lead to the formation of byproduct molecules. Starting from laboratory experiments, it is possible to infer the presence of molecules still undetected on TNOs. For instance, car-bonic acid (H 2 CO 3) is produced after irradiation of H 2 O:CO 2 icy mixtures, while irradiation of H 2 O:N 2 icy mixtures causes the production of N 2 O, NO, and NO 2 . From H 2 O:CH 4 :N 2 mixtures, many species are formed, such as CO, CO 2 , HCN, HNCO, N 2 O, and molecules including CN bonds. Moreover, ion irradiation may modify the relative intensity of NIR features, as in the case of solid methanol, whose 2.34 µm band decreases in intensity with respect to the...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009
Fulvio, D.; Sivaraman, B.; Palumbo, M. E. and Mason, N. J. (2009). Novel measurements of refracti... more Fulvio, D.; Sivaraman, B.; Palumbo, M. E. and Mason, N. J. (2009). Novel measurements of refractive index, density and mid-infrared integrated band strengths for solid O2, N2O and NO2: N2O4 mixtures. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 72(5), pp. 1007-1013. For guidance on citations see FAQs. c [not recorded] Version: [not recorded] Link(s) to article on publisher's website: http://dx.doi.org/
Science, 2006
Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution i... more Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.
Radiation Physics and Chemistry, 2004
Polyphenylacetylene (PPA) thin films deposited on silicon substrates have been bombarded with a b... more Polyphenylacetylene (PPA) thin films deposited on silicon substrates have been bombarded with a beam of 30 keV of He + ions. The radiation damage of the film has been monitored by FT-IR spectroscopy at fluences between 0.8 x 10 15 ions/cm 2 , 1.1 x 10 16 ions/cm 2 . The spectral changes undergone by the PPA film have been interpreted in terms of chain scission with formation of acetylenic and saturated end groups, in terms of crosslinking reaction and extensive radiolytic degradation. The expected cyclization reaction, a reaction which transforms a linear polymer into a ladder polymer has not been observed at all, although polystyrene (PS) is instead able to give this kind of reaction under somewhat similar conditions to those adopted in the present work. The initial aim to use the radiation damaged PPA as model compound for the study of the infrared spectra and the chemical structure of the organic matter present in certain astronomical objects known as protoplanetary nebulae has been frustrated by the unexpected results. In any case, it is probably the first time that the radiation resistance of PPA has been studied in a certain detail under the action of He + ions.
Radiation Effects and Defects in Solids, 1991
ABSTRACT The thickness of ice (H2O) layers accreted on a cold finger has been measured by detecti... more ABSTRACT The thickness of ice (H2O) layers accreted on a cold finger has been measured by detecting the interference pattern of a He-Ne laser beam (632.8 nm) reflected from the ice surface and from the underlying substrate.Sublimation and/or sputtering from the ice surface have been induced by bombarding the ice layers with 200 keV He ion beams. Sublimation rates and sputtering yields have been measured. It has been shown that if sublimation dominates then ice erosion is uniform and no light scattering is observed. If sputtering dominates, surface roughening, evidenced by light scattering, is observed.
Icarus, 1991
The thickness and survivability of a cosmic ray-generated primordial comet refractory mantle, or ... more 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
Topics in Applied Physics, 2006
Page 1. Vibrational Spectroscopy in Ion-Irradiated Carbon-Based Thin Films Giuseppe Compagnini1, ... more Page 1. Vibrational Spectroscopy in Ion-Irradiated Carbon-Based Thin Films Giuseppe Compagnini1, Orazio Puglisi1, Giuseppe A. Baratta2, and Giovanni Strazzulla2 ... 100, 505520 (2006) © Springer-Verlag Berlin Heidelberg 2006 Page 2. 506 Giuseppe Compagnini et al. ...
Radiation Physics and Chemistry, Mar 1, 2004
Polyphenylacetylene (PPA) thin films deposited on silicon substrates have been bombarded with a b... more Polyphenylacetylene (PPA) thin films deposited on silicon substrates have been bombarded with a beam of 30 keV of He + ions. The radiation damage of the film has been monitored by FT-IR spectroscopy at fluences between 0.8×10 19 and 1.1×10 20 ions/m 2. The spectral changes undergone by the PPA film have been interpreted in terms of chain scission with formation of acetylenic and saturated end groups, and in terms of crosslinking reaction and extensive radiolytic degradation. The expected PPA cyclization reaction, a reaction which transforms a linear polymer into a ladder polymer has not been observed, although polystyrene (PS) is able to give this kind of reaction under somewhat similar conditions to those adopted in the present work. The results have been discussed in an astrochemical context in relation to the infrared emission spectra of certain astrophysical object and molecules present in the interstellar medium.
Astron Astrophys, 2002
We have studied by infrared absorption spectroscopy the effects induced by fast ions (30 keV) and... more We have studied by infrared absorption spectroscopy the effects induced by fast ions (30 keV) and Lyman-alpha photons (10.2 eV) on some molecular ices at low temperature (10-20 K). It is well known that in both cases the physical and chemical properties of the ices are modified. However while the energy released by ions depends mainly on their energy and on the target species, the effects induced by photons also depend on the optical properties of the sample. Here we show that the effects of ion irradiation and UV photolysis are comparable on fresh ices (i.e. at low doses) but are increasingly different as processing is continued (i.e. at high doses).
Applied Physics Letters, Oct 12, 1992
Polarized Raman spectra have been performed in keV ion irradiated highly oriented pyrolytic graph... more Polarized Raman spectra have been performed in keV ion irradiated highly oriented pyrolytic graphite in order to investigate the disorder induced by energetic ions in the carbon matrix at room temperature. Early stages of ion irradiation (1012-1015 He+/cm2 3 keV) induce a high depolarization ratio of the 1360 cm-1 D line, leaving the 1580 cm-1 line almost unchanged. This was interpreted by an anisotropic damage induced in the highly oriented pyrolytic graphite structure by an ion collision cascade.
Journal of Geophysical Research Atmospheres, Nov 16, 2013
Infrared transmittance spectra of several volcanic ash samples positioned in the path of a IR bea... more Infrared transmittance spectra of several volcanic ash samples positioned in the path of a IR beam have been obtained. This technique is widely used in astronomy, in biological applications, in industrial and environmental fields. Nevertheless, in spite of its wide diffusion in several branch of science, up to now only few IR measurements on volcanic ash particles have been carried out in laboratory. In this work, infrared spectroscopy is used to investigate the spectral signature of volcanic ash particles emitted during the 21-24 July 2001 eruption at Mt. Etna, in Italy. A Bruker Equinox-55 FTIR interferometer operating in the range 1.43-16.67 µm is used to analyse the infrared transmittance of ash particles on KBr windows. For every collected spectrum, an image of the volcanic ash particles was recorded in the visible spectral range through the same microscope. These images are then analyzed by standard image analysis software in order to evaluate the main features of the particle...
Astronomy and Astrophysics
New experimental data demonstrating the transition from crystalline to amorphous water ice induce... more New experimental data demonstrating the transition from crystalline to amorphous water ice induced by keV ion-irradiation at temperatures between 10 and 80 K are presented. The procedure employed to monitor the structural changes is in situ IR spectroscopy. Results of some astrophysical applications show that such a process has to be considered when attempts to fit the astronomical spectra to those acquired in the laboratory are performed and especially when one attempts to deduce, from the shape of the observed ice band, information on the physical status, e.g., temperature history, of the responsible dust.
Some results, obtained from laboratory experiments of ion irradiation of ice mixtures containing ... more Some results, obtained from laboratory experiments of ion irradiation of ice mixtures containing H, C, N, and O bearing species are here summarized. They, in particular the formation of CN-bearing species, are relevant to the formation and evolution of complex organics on interstellar dust and small bodies in the external Solar System. Material incorporated into primitive Solar System bodies and delivered to the early Earth, may have contributed to the origin of life. The delivery of CN-bearing species seems to have been necessary because molecules containing the cyanogen bond are difficult to be produced in an environment that is not strongly reducing as that of the early Earth probably was. We report also on an ongoing research program concerning the interaction between refractory materials produced by ion irradiation of simple ices and biological materials (amino acids, proteins, celles), Perspective for possible future work is also given.
Ices, silicates, and carbonaceous materials have been observed in different astrophysical environ... more Ices, silicates, and carbonaceous materials have been observed in different astrophysical environments such as the interstellar medium, circumstellar regions, comets, and solid surfaces of Solar System objects. In space these materials suffer from processing caused by cosmic rays, photons and thermal annealing. Our knowledge of the effects of processing on the evolution of solids in different astrophysical environments in mainly based on laboratory experiments. The Laboratory of Experimental Astrophysics in Catania (Italy) is equipped to study the effects of processing on astrophysical relevant materials. Here we briefly describe the experimental set up and discuss some recent results.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014
In this paper we present the formation of carbon nanowires (polyynes and polycumulenes) in the so... more In this paper we present the formation of carbon nanowires (polyynes and polycumulenes) in the solid state by ion irradiation of frozen hydrocarbons (C 6 H 6 and C 2 H 2 ). Irradiations have been performed using H + ions in the 100's keV energy regime using fluences up to 5 Â 10 14 ions/cm 2 . Beyond the intrinsic significance of these results in the field of material science, this work has been motivated by the fact that ion beam irradiation of hydrocarbon ices is one of the most important process thought to happen in several extraterrestrial environments where many spectroscopic features of polyyne molecules have been identified.
The study of the evolution of organic matter subjected to space conditions, and more specifically... more The study of the evolution of organic matter subjected to space conditions, and more specifically to solar photons in the vacuum ultraviolet range (120-200 nm) has been undertaken in low Earth Orbit since the 90's, and implemented on various space platforms. The most recent exposure facilities are BIOPAN outside the Russian automatic capsules FOTON, and EXPOSE-E & -R (1&2) outside the International Space Station. They allow the photolysis of many different samples simultaneously, and provide us with valuable data about the formation and evolution of organic matter in the Solar System (meteorites, comets, Titan's atmosphere, the Martian surface...) and in the Interstellar Medium. They have been used by European teams in the recent past "Experimental astrochemistry: from ground-based to space-borne laboratories", University of Liège (Belgium), 2-3 July 2014, ed. M. De Becker 60 Bulletin de la Société Royale des Sciences de Liège, Vol. 84, 2014, p. 60 -73 (ORGANIC on BIOPAN V-FOTON M2 and UVolution on BIOPAN VI-FOTON M3, PROCESS on EXPOSE-E, AMINO and ORGANICS on EXPOSE-R), and a new EXPOSE set is currently exposed outside the ISS (PSS on EXPOSE-R2). These existing tools are very valuable; however, they have significant limitations that limit their capabilities and scientific return. One of the most critical issues for current studies is the lack of any in-situ analysis of the evolution of the samples as a function of time. Only two measurements are available for the experiment: one before and one after the exposure. A significant step forward has been achieved with the O/OREOS NASA nanosatellite and the OREOcube ESA project with onboard UV-visible measurements. However, for organic samples, following the evolution of the samples would be more informative and provide greater insight with infrared measurements, which display specific patterns characteristic of major organic functionalities in the mid-infrared range (4000-1000 cm −1 ).
Vis–NIR spectra of some Centaurs and Trans-Neptunian Objects (TNOs) indi-cate surfaces rich in H ... more Vis–NIR spectra of some Centaurs and Trans-Neptunian Objects (TNOs) indi-cate surfaces rich in H 2 O, N 2 , CO 2 , CH 4 e CH 3 OH. Cosmic ion irradiation is one of the processes driving the evolution of TNO surfaces. A main role is played by the chemistry induced by colliding ions; many molecular bonds are broken along the ion track, and this may lead to the formation of byproduct molecules. Starting from laboratory experiments, it is possible to infer the presence of molecules still undetected on TNOs. For instance, car-bonic acid (H 2 CO 3) is produced after irradiation of H 2 O:CO 2 icy mixtures, while irradiation of H 2 O:N 2 icy mixtures causes the production of N 2 O, NO, and NO 2 . From H 2 O:CH 4 :N 2 mixtures, many species are formed, such as CO, CO 2 , HCN, HNCO, N 2 O, and molecules including CN bonds. Moreover, ion irradiation may modify the relative intensity of NIR features, as in the case of solid methanol, whose 2.34 µm band decreases in intensity with respect to the...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009
Fulvio, D.; Sivaraman, B.; Palumbo, M. E. and Mason, N. J. (2009). Novel measurements of refracti... more Fulvio, D.; Sivaraman, B.; Palumbo, M. E. and Mason, N. J. (2009). Novel measurements of refractive index, density and mid-infrared integrated band strengths for solid O2, N2O and NO2: N2O4 mixtures. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 72(5), pp. 1007-1013. For guidance on citations see FAQs. c [not recorded] Version: [not recorded] Link(s) to article on publisher's website: http://dx.doi.org/
Science, 2006
Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution i... more Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.
Radiation Physics and Chemistry, 2004
Polyphenylacetylene (PPA) thin films deposited on silicon substrates have been bombarded with a b... more Polyphenylacetylene (PPA) thin films deposited on silicon substrates have been bombarded with a beam of 30 keV of He + ions. The radiation damage of the film has been monitored by FT-IR spectroscopy at fluences between 0.8 x 10 15 ions/cm 2 , 1.1 x 10 16 ions/cm 2 . The spectral changes undergone by the PPA film have been interpreted in terms of chain scission with formation of acetylenic and saturated end groups, in terms of crosslinking reaction and extensive radiolytic degradation. The expected cyclization reaction, a reaction which transforms a linear polymer into a ladder polymer has not been observed at all, although polystyrene (PS) is instead able to give this kind of reaction under somewhat similar conditions to those adopted in the present work. The initial aim to use the radiation damaged PPA as model compound for the study of the infrared spectra and the chemical structure of the organic matter present in certain astronomical objects known as protoplanetary nebulae has been frustrated by the unexpected results. In any case, it is probably the first time that the radiation resistance of PPA has been studied in a certain detail under the action of He + ions.
Radiation Effects and Defects in Solids, 1991
ABSTRACT The thickness of ice (H2O) layers accreted on a cold finger has been measured by detecti... more ABSTRACT The thickness of ice (H2O) layers accreted on a cold finger has been measured by detecting the interference pattern of a He-Ne laser beam (632.8 nm) reflected from the ice surface and from the underlying substrate.Sublimation and/or sputtering from the ice surface have been induced by bombarding the ice layers with 200 keV He ion beams. Sublimation rates and sputtering yields have been measured. It has been shown that if sublimation dominates then ice erosion is uniform and no light scattering is observed. If sputtering dominates, surface roughening, evidenced by light scattering, is observed.