where
is the cross-section and
the reduced mass of the
system. The present excitation and de-excitation rates are given in
Tables 2-5 for 4 temperatures: 300 K, 500 K, 1000 K and 1500 K. Collision rate coefficients
for other temperatures are available on request from one of us
(Evelyne.Roueff@obspm.fr).
To the best of our knowledge, there is no previous calculation or experiment to which the present results could be compared. It is all the more important to stress the excellent agreement between the new data and those obtained in our previous pure rotational excitation study based on the rigid rotor approximation (Roueff & Zeippen [1999]). This shows that the coupling between rotation and vibration is negligible for the ground state. A typical example is displayed in Fig. 1 for the rotational de-excitation of the first three rotational levels as a function of the relative velocity between HD and He.
T(K) | He | H | H2 | |
300 | 1.0(-16) | 5.7(-15) | 5.8(-17) | |
500 | 9.8(-16) | 2.6(-14) | 3.4(-16) | |
1000 | 2.1(-14) | 3.4(-13) | 8.1(-15) | |
1500 | 1.2(-13) | 3.5(-12) |
Copyright The European Southern Observatory (ESO)