DETERMINING THE DENSITY-OF-STATES AND PARTITION-FUNCTION FOR POLYATOMIC-MOLECULES

Absolute thermodynamic properties can be extracted for complex molecul es which are described algebraically. By exploiting some group theoret ical properties of the Hamiltonians, which often include large anharmo nicities, the partition function, and properly normalized density of s tates can be found. When the first few energies of the system are know n, one can extend the results accurately to zero temperature. Examples are given for diatomic molecules as well as the polyatomic molecule C 2H2.