The accuracy of second order perturbation theory for multiply excited vibrational energy levels and partition functions for a symmetric top molecular ion J. Chem. Phys. 98, 4948 (1993); 10.1063/1.464950 Semiclassical vibrational eigenvalues of triatomic molecules: Application of the FFT method to SO2, H2O, H+ 3, and CO2 J. Chem. Phys. 81, 2394 (1984); 10.1063/1.447939 Coupled equations applied to the photodissociation of linear triatomics: A test of approximate schemes for calculating the line shape and the effect of final states interactions J. Chem. Phys. 67, 4983 (1977); 10.1063/1.434719Energy partitioning and isotope effects in the fragmentation of triatomic negative ions: Monte Carlo scheme for a classical trajectory study Various approximate schemes are used to obtain vibrational energy levels and partition functions for H,O and SO,. These results are then compared with accurate quantum mechanical values computed for the same original quartic force fields. The neglect of interaction force constants in internal coordinates and the use of a Morse model to describe stretching anharmonicity are both shown to provide reasonably accurate perturbation theory energy levels and partition functions, while the neglect of interaction force constants in normal coordinates is found to yield much less accurate results. In addition, the method of Pitzer and Gwinn to calculate partition functions without first calculating energy levels is shown to provide a good approximation to the accurate partition functions.

If Wegner's model is correct, then the /3-carotene results suggest that stacks of conjugated segments of (CH), occur in the absence of chain folding and, after doping, are involved in charge transfer perpendicular to the segment axes.

For a potential of different shape the critical value might change as much as 25% and, of course, the diatom potential might be modified in solution. However, these changes surely cannot offset the very small B value, and we may conclude that 3HeT definitely has no bound state. An ionic complex appeared much more likely to be capable of binding 3He, and our calculations confirm that such complexes indeed have appreciable stability.At the storage temperature of 20 K, only a modest enthalpy increase for an He-ionic complex as compared to a neutral He-T2 interaction could account for the observed supersolubility. This can be seen by considering the equilibrium constants for dissolving He in liquid tritium without (unprimed) and with (primed) ionic complexes present: K = [He-neutral] / [He(gas)] K'= [He-ionic] / [He(gas) ] If we assume that the standard entropy change and the (20)

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