A High-Temperature Partition Function for H 3 +
Abstract
{H}^{+}3 is the main supplier of electrons to metal-free stars below ~8000 K. To describe {H}^{+}3 properly it is important to know its partition function. Previous determinations of this function are based on extrapolations from lower temperatures. A new partition function is presented that is calculated by explicit ab initio computation of levels lying up to 15,000 cm-1 above the ground state and with J <= 20. The effect of all other bound levels of {H}^{+}3 , which is significant at higher temperatures, is included using a simple model based on Pade approximants. The new partition function is very significantly larger (up to a factor of 100 in some cases) than previous estimates above 3000 K.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1995
- DOI:
- 10.1086/309789
- Bibcode:
- 1995ApJ...454L.169N
- Keywords:
-
- MOLECULAR DATA;
- STARS: ATMOSPHERES