The vibrational energy pattern in acetylene (VI): Inter- and intrapolyad structures

Intra- and interpolyad structures are investigated in the vibrational energ y pattern of acetylene, using the spectroscopic Hamiltonian presented in pr evious papers in this series [see El Idrissi , J. Chem. Phys. 110, 2074 (19 99)]. The existence of two constants of the motion is shown to generate ver y regular patterns in the manifold of vibrational energy levels. Distinct r egular and oscillatory contributions are evidenced in the number of vibrati onal levels in the main polyads, which are fully reproduced using the gener ating function presented in Sadovskii and Zhilinskii [J. Chem. Phys. 103, 1 0520 (1995)]. Further developments of this approach are outlined. (C) 2000 American Institute of Physics. [S0021-9606(00)01442-2].