Ro-vibrational Transition Energies and Absorption Intensities of the 1A1 States of H2O, He2O2+ and He2S2+

Variational ro–vibrational wave functions are calculated using an Eckart–Watson Hamiltonian, which has embedded an ab initio potential energy function. These wave functions, together with an ab initio dipole moment function, are employed to predict transition energies and absorption intensities. The radiative transition probability integrals are determined using a novel adaptation of the Harris–Engerholm–Gwinn integration scheme. The method and solution algorithm yields results in excellent agreement with previously determined experimental and theoretical electric dipole allowed transitions for the 1 A 1 ground state of H 2 O. The method has also been applied to the 1 A 1 states of the helide analogs of water, namely He 2 O 2+ and He 2 S 2+ , in order to predict their ro–vibrational transition energies and absorption intensities, thereby facilitating their possible interstellar detection.