All Figures

	Figure 1: Cross sections for positronium formation, ionization and excitation in positron collision with a) atomic hydrogen; b) molecular hydrogen; and  c) helium as a function of the kinetic energy.
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In the text

	Figure 2: Fraction of positrons forming positronium in flight (f1) by charge exchange with atomic hydrogen as a function of the ionization fraction (y) in a warm component of the interstellar medium (electron density:  cm-3, electron temperature:  K) and in solar flare (  cm-3,  K). The results presented in Fig. 2 of BRD79 are shown for comparison.
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In the text

	Figure 3: Positron reaction rates as a function of temperature.
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In the text

	Figure 4: Collisions and subsequent annihilation of positrons with grains (of various sizes and types) - a) positron re-emission; b) positron backscattering; c) positronium in grain, d) positronium ejection.
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In the text

	Figure 5: Annihilation spectra for the 5 ISM phases separately (see text): a) cold, molecular hydrogen medium; b) cold, atomic hydrogen medium; c) warm, neutral medium; d) warm, ionized medium; e) hot medium.
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In the text

Figure 6: Combined ("global'') ISM annihilation spectra, obtained under two assumptions: 1) positrons annihilating in all phases according to the filling factors and densities given in the McKee & Ostriker (1977) model, either with or without the effect of the grains (solid, blue dashed and red dotted curves); 2) positrons not annihilating in the cold phases, with/without grain effect (solid and dotted narrower purple curves).

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In the text