High resolution FTIR spectra of AsD3 in the 20-1000 cm(-1) region. The ground, v(2)=1 and v(4)=1 states

The pure rotational spectrum of the near-spherical oblate symmetric top AsD 3 has been recorded in the 20-120cm(-1) region with a resolution of 2.3 x 1 0(-3) cm(-1) employing an FT interferometer. Rotational transitions with 5 less than or equal to J less than or equal to 29 and 0 less than or equal t o K less than or equal to 25 of the ground state (GS) and the v(2) = 1 and v(4) = 1 excited states have been assigned. Splittings were observed for th e GS, K = 3 and 6 levels, the K = 3 levels of v(2) and the kl = -2, 1, 4 an d 7 levels of v(4). Furthermore the x, y Coriolis coupled v(2) and v(4) ban ds, v(2) = 654.4149cm(-1), and v(4)(0) = 714.3399 cm(-1), have been examine d with a resolution of 2.4 x 10(-3) cm(-1), and ca. 2500 allowed and 336 'f orbidden' lines with J(max)' = 31 and K-max' = 28 have been assigned. max m ax Appropriately weighted GS data comprising FIR lines, allowed and 'forbid den' (up to Delta K = +/-6) CS combination differences, mmw data, and Delta J = 0, Delta K = +/-1 distortion moment transitions were fitted together, and GS parameters complete through H parameters have been determined. Two d ifferent reductions of the Hamiltonian, either with Delta K = +/-6 (h(3)) o r Delta K = +/-3(epsilon) off-diagonal elements, have been employed. Equiva lence of these reductions up to J = 22 was established while for J > 22 the epsilon reduction is superior. The v(2) and v(4) data have been fitted wit h two equivalent models based on different reductions of the rovibrational Hamiltonian. In addition to the dominating x, y Coriolis resonance, zeta(24 )(y) 0.520, Delta(k - l) = +/-3 and +/-6 interactions are important and wer e accounted for by the models. The transition moment ratio \ M-4: M-2\ = 0. 75 has been determined, with a positive sign of the product M(2)zeta(24)(y) M(4) An improved r(0) structure, r(0)(AsD) = 1.51753 Angstrom and alpha(0)( DAsD) = 92.000 degrees, has been determined.