ANALYSIS OF DYAD - DYAD TRANSITIONS OF (CH4)C-12 AND (CH4)C-13

This work is a refinement of the (0100) and (0001) state description for both isotopes (CH4)-CH-12 and (CH4)-CH-13. We introduce recently observed dyad - dyad lines in addition to "pure rotational" and infrared transitions in a simultaneous fit of the ground-and upper-state parameters. Using a sixth-order-reduced Hamiltonian, significant improvements are achieved for the upper-state parameters that were previously retrieved from infrared transitions only. As a result, substantially more accurate predictions of the dyad - dyad spectrum of both isotopes are reported in the frequency range 0 - 300 GHz with a strength greater than 10(-11) cm-2 atm-1 at 296 K.