Deuterated hydrogen chemistry: Partition functions, equilibrium constants and transition intensities for the H3+ system

Abstract

H3+ and the deuterated isotopomers are thought to play an important role in interstellar chemistry. The partition functions of H3+, D2H+ and D3+ are calculated to a temperature of 800 K by explicitly summing the ab initio determined rotation-vibration energy levels of the respective species. These partition functions are used to calculate the equilibrium constants for nine important reactions in the interstellar medium involving H3+ and its deuterated isotopomers. These equilibrium constants are compared with previously determined experimental and theoretical values. The Einstein A coefficients for the strongest dipole transitions are also calculated.