Solar wind charge exchange in cometary atmospheres - I. Charge-changing and ionization cross sections for He and H particles in H2O

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Volume 630 (October 2019)

A&A, 630 (2019) A35

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Table A.1

Recommended charge-changing cross sections for (He²⁺, He⁺, and He⁰) projectiles colliding with H₂O vapor between 100 and 5000 km s⁻¹ of impact speed.

Speed	Energy	Helium–H₂O cross sections
(km s⁻¹)	(keV amu⁻¹)	(m²)


100	0.052	1.62E-20	1.03E-19	2.80E-28^*	1.08E-19^*	9.3E-37^*	8.4E-25^*
150	0.117	2.74E-20	8.46E-20	2.34E-27^*	7.91E-20	8.0E-34^*	7.8E-24^*
200	0.209	3.92E-20	6.65E-20	1.06E-26^*	6.37E-20	6.4E-32^*	3.2E-23^*
250	0.326	5.12E-20	5.40E-20	3.47E-26^*	5.66E-20	1.5E-30^*	8.9E-23^*
300	0.470	6.28E-20	4.58E-20	9.12E-26^*	5.36E-20	1.7E-29^*	1.9E-22^*
350	0.639	7.39E-20	4.02E-20	2.07E-25^*	5.29E-20	1.2E-28^*	3.5E-22
400	0.835	8.43E-20	3.65E-20	4.19E-25^*	5.33E-20	5.7E-28^*	5.8E-22
450	1.06	9.39E-20	3.39E-20	7.81E-25^*	5.45E-20	2.2E-27^*	8.7E-22
500	1.30	1.03E-19	3.21E-20	1.36E-24^*	5.61E-20	6.9E-27^*	1.2E-21
550	1.58	1.10E-19	3.08E-20	2.24E-24^*	5.80E-20	1.9E-26^*	1.7E-21
600	1.88	1.17E-19	3.00E-20	3.52E-24^*	5.99E-20	4.6E-26^*	2.2E-21
700	2.56	1.29E-19	2.90E-20	7.80E-24^*	6.38E-20	2.0E-25^*	3.4E-21
800	3.34	1.37E-19	2.88E-20	1.54E-23^*	6.72E-20	6.7E-25^*	4.8E-21
900	4.23	1.42E-19	2.88E-20	2.77E-23	6.99E-20	1.8E-24^*	6.4E-21
1000	5.22	1.45E-19	2.90E-20	4.64E-23	7.17E-20	4.3E-24^*	8.1E-21
1250	8.16	1.44E-19	2.95E-20	1.34E-22	7.27E-20	2.2E-23^*	1.3E-20
1500	11.7	1.36E-19	2.92E-20	3.05E-22	6.94E-20	7.1E-23^*	1.7E-20
1750	16.0	1.24E-19	2.77E-20	5.89E-22	6.32E-20	1.7E-22^*	2.1E-20
2000	20.9	1.11E-19	2.52E-20	1.01E-21	5.56E-20	3.4E-22^*	2.5E-20
2500	32.6	8.44E-20	1.84E-20	2.29E-21	4.03E-20	9.1E-22^*	3.0E-20
3000	47.0	6.22E-20	1.15E-20	4.12E-21	2.76E-20	1.7E-21^*	3.3E-20
3500	63.9	4.50E-20	6.31E-21	6.31E-21	1.84E-20	2.7E-21^*	3.5E-20
4000	83.5	3.23E-20	3.11E-21	8.65E-21	1.22E-20	3.6E-21	3.5E-20
4500	105.7	2.31E-20	1.40E-21	1.09E-20	8.05E-21	4.4E-21	3.5E-20
5000	130.5	1.66E-20	5.85E-22	1.28E-20	5.34E-21	5.0E-21	3.4E-20

Notes. Energies in keV amu⁻¹ are given for reference. “E±XX” refers to × 10^±XX. Values marked by an asterisk are smoothly extrapolated from the fits. Uncertainties are indicated in superscript as ^(a) < 25%, ^(b) 25− 75%, ^(c) > 75%.

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