Table 3
Recommended ionization cross-section polynomial fits for (He2+, He+, He0) projectiles colliding with H2O vapor.
| Cross section | Degree | Coefficients | Validity range | Confidence | |||||
|---|---|---|---|---|---|---|---|---|---|
| (m2) | n | p0 | p1 | p2 | p3 | p4 | vi (km s−1) | Ei (keV u−1) | |
| σ22 | 4 | − 265.3697 | 176.7016 | − 48.3734 | 5.91427 | − 0.27030 | 1400−10 000 | 10.0−520 | High |
| σ11 | 4 | − 169.8607 | 108.1412 | − 29.7492 | 3.66917 | − 0.16967 | 450−10 000 | 1.06−520 | High |
| σ00 | 4 | − 87.3445 | 49.6893 | − 14.1573 | 1.82417 | − 0.08824 | 450−10 000 | 1.06−520 | Low |
Notes. The polynomial, function of the speed of the impactor, is of the form
, where n is the degree of the fit, the speed vi is expressed in m s−1 and the cross section σ in m2. Ranges of validity for impact speeds and energies are given. Confidence levels on the fits are indicated as high (< 25%), medium (25– 75%), and low (> 75%) (see text).
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