A POTENTIAL-ENERGY SURFACE FOR THE ELECTRONIC GROUND-STATE OF H2TE DERIVED FROM EXPERIMENT

We report here the determination of a new potential energy surface for the electronic ground state of the H2Te molecule by fitting to an ext ensive set of very recent experimental spectroscopic data (see J.-M. F laud, P. Areas, H. Bilrger, O. Polanz, and L. Halonen, J. Mol. Spectro sc. 183, 310-335 (1997), and references therein) by means of the MORBI D (Morse Oscillator Rigid Bender Internal Dynamics) computer program. The fitting to all 1111 input data (involving rotation-vibrational sta tes with J less than or equal to 10) had a standard deviation of 0.18 cm(-1) and was obtained by varying 14 parameters. With the new potenti al energy function, the rotation-vibration energies of (H2Te)-Te-130 h ave been calculated with the MORBID program. In particular, we have ca lculated the rotational energy manifolds for J less than or equal to 4 0 in the lowest vibrational states. Compared to previous potential ene rgy functions for H2Te, the new function has substantially improved th e reproduction of the rotational spacings in the excited vibrational s tates. An important aim of the present work is the further characteriz ation of the anomalous ''fourfold cluster effect'' (i.e., the formatio n of four-member groups of nearly degenerate rotation-vibration energi es at high rotational excitation) exhibited by the energy levels of H2 Te. Comparison of our theoretical results with the experimental result s of J.-M. Flaud, M. Betrencourt, P. Areas, Il. Burger, O. Polanz, and W. J. Lafferty (1997, J. Mel. Spectrosc. 182, 396-420) provides concl usive evidence for the existence of so-called Type II clusters (cluste rs formed by coalescence of two energy doublets belonging to two diffe rent vibrational states) in the nu(1)/nu(3) vibrational states of (H2T e)-Te-130. (C) 1997 Academic Press.