STRUCTURES AND SPECTROSCOPIC CONSTANTS OF SOME PROTONATED GROUP VIA MOLECULES

Author Institution: Molecular Spectroscopy Division, National Bureau of Standards; Molecular Spectroscopy Division, National Bureau of StandardsWe report the results of theoretical calculations of the proton affinities and structures of several series of molecules containing Group VIA atoms. The series studied included CX, OCX, XCX, and $H_{2}CX$ where X-O, S, Se, Te. In those cases where multiple protonation sites are available, a definitive assignment of the most stable site was determined. Excellent agreement with the experimentally measured proton affinities is found in most cases. These results indicate that the intuitive chemical trend which one would expect as one moves down a column of the periodic table is upheld, with a large change on going from the first to the second row. In addition, we report calculated vibrational frequencies for both neutral and protonated systems. Calculations were performed at both the SCF and CIDS levels with full geometry optimizations at the SCF level. Basis sets were of at least $DZ\cdot P$ quality. The effect of the chemically unimportant core electrons in these systems was represented by compact effective potentials