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*Astron. Astrophys. 328, 617-627 (1997)*
## Appendix A: collision rates ^{} O ^{} O-He
To obtain the de-excitation rates of ^{16} O^{18}
O-He, the collisional transitions are separated into 9 groups:
For each group, N indicates the initial level, N', the final one
and and we have used the following hypothesis
to obtained the de-excitation rates:
- For odd values of
*N* and , the
rates are equal to those of O_{2}.
- For odd values of
*N* and even values of
, the rates are obtained by averaging the rates
of the transition and the transition
. For odd values of *N* and
( =0, =1), the rates are
obtained by extrapolation from all the rates from the same *N* to
0.
- For even values of
*N* and (even
values of ), the rates are obtained by averaging
the rates of *N* -1 and *N* +1 (equal to those of
O_{2}) for the same value of . For even
values of *N* and ( =0,
=1), the rates are obtained by extrapolation
from all the rates with the same value of and
0.
- For even values of
*N* and odd values of
, the rates are obtained by averaging the rates
of the transition and transition
.
The excitation rates are obtained by the usual reversibility law
and the collisional rates of ^{16} O^{18}
O-H_{2} are equal to those of ^{16} O^{18}
O-He multiplied by the reduced mass factor (see
MVB).
© European Southern Observatory (ESO) 1997
Online publication: March 26, 1998
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