= | (6) | ||

= | |||

((X-X_{k})/(X_{k}-1))) |

where

= | F_{2}+F_{3}/(X-X_{k}+1) |
(7) | |

= | |||

((X-X_{k})/(X_{k}-1))) |

where

= | F_{3}/(X-X_{k}+F_{2})^{2} |
(8) | |

= | |||

((X-X_{k})/(X_{k}-1))) |

where

=1 | (9) |

= 1. |

We note the inclusion of the line strength in the definition of type 1. If high energy data is correct and consistent with the line strength then

Figures 4a-c show the
ratio and *B*-*C* plots for the spin change hydrogen molecular reaction
cross-section
.
The source data
are from Behringer & Fantz (1996) and are themselves a fit to very limited experimental
data (Mohlmann & De Heer 1976). The ratio plot seems to indicate that the first data value is too low, while the
last two data values suggest that there is some deviation (again too low) from the
expected high energy behaviour. The *B*-*C* plot for these data (Fig. 4b) shows that the
spline diverges at both limits for reasonable values of the parameters. In Fig. 4c,
the first and last two data points have been adjusted (see Sect. 6 below) and an
optimised fit then obtained. These adjustments are well outside the range of the original
experimental data and perhaps deliver a safer extrapolation in the limiting asymptotic
and threshold regions.

Figure 5:
An editable graph window with an active B-C plot. The number pair at the bottom of the
displayed graph shows the cursor position, in graph coordinates, when a point is being moved |

Copyright The European Southern Observatory (ESO)