All Figures

$\begin{figure} \par\resizebox{18cm}{!}{\includegraphics[clip]{h4537f1.eps}} \end{figure}$ Figure 1: Schematic view of the experimental apparatus used for in situ Raman spectroscopy of ion irradiated frozen gases.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f2.eps}} \end{figure}$ Figure 2: IR (top curve) and Raman spectra of a pure methane frozen film before (curve a) and after (curves b-d) irradiation with He⁺ (30 keV) and Ar⁺⁺ (60 keV) ions. Spectrum a (corresponding to the mixture as deposited) has been arbitrarily shifted with respect to the other Raman spectra for clarity. Curves b, c and d represent the spectra, at 100 K, after increasing irradiation doses (130, 290 and 1000 eV/16 amu respectively).
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f3.eps}} \end{figure}$ Figure 3: IR (top curve) and Raman spectra of the mixture H₂O:CH₄:N₂ before (curve a) and after (curves b and c, corresponding to doses of 378 eV/16 amu and 825 eV/16 amu respectively) irradiation with He⁺ (30 keV) ions at low temperature (12 K). In spectra b and c the ice features are undetectable because of the intense fluorescence background. The arrow in the IR spectrum indicates the position of the N $\equiv$ N symmetric stretching mode, which cannot be observed.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{h4537f4.eps}} \end{figure}$ Figure 4: G and D Raman bands of the mixture H₂O:CH₄:N₂ after irradiation with He⁺ (30 keV) ions at 12 K. From top to bottom the spectra are displayed in order of increasing irradiation dose. For each spectrum the Lorentzian fit, with the two components, is shown. The corresponding parameters (peak position, full width at half maximum ( FWHM) and the intensity ratio of the G and D lines) are listed on the right side of the figure.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f5.eps}} \end{figure}$ Figure 5: Raman spectra, at room temperature, of the residue obtained after ion irradiation of the mixture H₂O:CH₄:N₂ at 12 K before (top curve) and after (bottom curve) irradiation with 30 keV He⁺ ions. It is evident that the fluorescence background greatly decreases after irradiation.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f6.eps}} \end{figure}$ Figure 6: G and D Raman bands of the residue of the mixture H₂O:CH₄:N₂ before (top curve) and after (bottom curve) irradiation with He⁺ (30 keV) ions at room temperature. For each spectrum the Lorentzian fit, with the two components, is shown. The corresponding parameters (peak position, Full Width at Half Maximum ( FWHM) and the intensity ratio of the G and D lines) are listed on the right hand side of the figure.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f7.eps}} \end{figure}$ Figure 7: IR (top curve) and Raman spectra of the mixture CH₃OH:N₂ before (curve a) and after (curve b) irradiation with He⁺ (30 keV) ions. The fluorescence continuum increases after ion irradiation, but no band appear which can be attributed to the amorphous carbon. The apparent jumps from a spectral region to another indicate laser induced alteration of the sample.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f8.eps}} \end{figure}$ Figure 8: D line full width at half maximum ( FWHM) versus peak position. The stars, all in the middle-bottom part of the figure, refer to IDPs. The label 1 on the squares indicates the mixture H₂O:CH₄:N₂ at 12 K at the first irradiation dose, while 2 and 3 refer to the same sample at increasing irradiation dose. The same criterion is adopted for the corresponding residue, which is represented by the up triangles and is labelled with 4 and 5 respectively before and after irradiation. Labels ach2 irr and acarh irr refer to ACH2 and ACAR_H grains, respectively, after ion irradiation.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f9.eps}} \end{figure}$ Figure 9: G line full width at half maximum ( FWHM) versus peak position. All the symbols in the graph have the same meaning as in the previous figure.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f10.eps}} \end{figure}$ Figure 10: $I_{\rm D}/I_{\rm G}$ ratio versus G line full width at half maximum ( FWHM) for the laboratory samples discussed in this work and 11 IDPs. All the symbols in the graph have the same meaning of the previous figure.
Open with DEXTER

In the text

$\begin{figure} \par\resizebox{18cm}{!}{\includegraphics[clip]{h4537f1.eps}} \end{figure}$	Figure 1: Schematic view of the experimental apparatus used for in situ Raman spectroscopy of ion irradiated frozen gases.
Open with DEXTER

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f5.eps}} \end{figure}$	Figure 5: Raman spectra, at room temperature, of the residue obtained after ion irradiation of the mixture H₂O:CH₄:N₂ at 12 K before (top curve) and after (bottom curve) irradiation with 30 keV He⁺ ions. It is evident that the fluorescence background greatly decreases after irradiation.
Open with DEXTER

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f7.eps}} \end{figure}$	Figure 7: IR (top curve) and Raman spectra of the mixture CH₃OH:N₂ before (curve a) and after (curve b) irradiation with He⁺ (30 keV) ions. The fluorescence continuum increases after ion irradiation, but no band appear which can be attributed to the amorphous carbon. The apparent jumps from a spectral region to another indicate laser induced alteration of the sample.
Open with DEXTER

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f9.eps}} \end{figure}$	Figure 9: G line full width at half maximum ( FWHM) versus peak position. All the symbols in the graph have the same meaning as in the previous figure.
Open with DEXTER

$\begin{figure} \par\resizebox{8.5cm}{!}{\includegraphics[clip]{h4537f10.eps}} \end{figure}$	Figure 10: $I_{\rm D}/I_{\rm G}$ ratio versus G line full width at half maximum ( FWHM) for the laboratory samples discussed in this work and 11 IDPs. All the symbols in the graph have the same meaning of the previous figure.
Open with DEXTER