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.
Infrared and Raman spectra and a complete assignment of vibrational fundamentals are presented for cis- and trans-1,2-difluoroethylenes and their deuterated modifications. For cis-CFHCFH the fundamentals are: (a1) 3122, 1716, 1263, 1015, 237; (a2) 839, 495; (b1) 3136, 1374, 1130, 769; and (b2) 756 cm−1. For trans-CFHCFH the fundamentals are: (ag) 3111, 1694, 1286, 1123, 548; (au) 875, 329; (bg) 788; and (bu) 3114, 1274, 1159, 341 cm−1. The near degeneracy in ν7 and ν12 of the trans isomer is shown from low-temperature crystal and matrix studies and zero-order normal coordinate calculations. Analysis of the rotational structure in the region of the overlapped bands proves that these fundamentals are strongly perturbed by Coriolis coupling. From the vibrational fundamentals and a previous measurement of ΔH°650, the cis isomer is shown to have 1086 cal/mole less electronic energy than the trans isomer. For the in-plane vibrations refined Urey–Bradley potential constants are presented. These constants are obtained from an overlay calculation involving the full set of six molecules. For the out-of-plane vibrations, refined general valence constants, obtained for the separate isomers, are presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.