Radiolysis of H2O:CO2 ices by heavy energetic cosmic ray analogs

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Volume 523 (November-December 2010)

A&A, 523 (2010) A77

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Table 2

Dissociation cross section, radiochemical yield, and sputtering values of H₂O and CO₂ obtained from the radiolysis of pure water ice and mixed water-CO₂ ices by 52 MeV Ni ions.

Species	Mixture	σ _d	−G_d	N _∞	Y	L^‡	N ₀	Model
	(H₂O:CO₂)	(10^-13 cm²)	molec/100 eV	(10¹⁷ molec cm^-2)	(10⁴ molec ion^-1)	(10⁴ molec ion^-1)	(10¹⁷ molec cm^-2)

H₂O	(1:0)	1.1	7.48	12	1^a	14	15	1
	(10:1)	~1	4.90	~4	1^a	~5	6.9	2
	(1:1)	1.0	6.35	3.0	1^a	4.0	5.9	3
CO₂	(0:1)	1.8	6.90	NA^†	2.2	0	9.1	4
	(1:1)	1.6	7.84	NA	1.2^b	0	6.2	5a
	(1:1)	2.1	10.3	NA	0^c	0	6.2	5b
	(10:1)	~1	6.35	NA	~0.2^d	0	~0.8	6a
	(10:1)	~0.7	4.45	NA	0^c	0	~0.8	6b

Notes.

^(a)

Taken from Brown et al. (1984).

^(b)

Estimated to be a half of the value determined from pure CO₂ ice.

^(c)

No CO₂ sputtering. Assuming that the water layering is high enough to fully cover the CO₂ molecules on the surface.

^(d)

Estimated to be a tenth of the value determined from pure CO₂ ice.

^(†)

NA = Not applicable.

^(‡)

For H₂O: derived from L = N_∞σ_d + Y. For CO₂: assuming no layering from residual CO₂.

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