The hydrogen-bonded cluster anions Br-center dot center dot center dot HCCH and I-center dot center dot center dot HCCH: results of coupled cluster calculations

Large-scale coupled cluster calculations at the CCSD(T) level of approximat ion have been carried out for the anionic complexes Br-. . . HCCH and I-. . . HCCH, both of which have a linear equilibrium structure. The equilibrium dissociation energies (D-e) are predicted to be 3126 and 2550 cm(-1), resp ectively. Agreement with available experimental data, obtained through pred issociation infrared spectroscopy, is very good. In addition, many predicti ons are made for spectroscopic properties of various isotopomers of the two species. Particular emphasis is given to the effects of vibrational anharm onicity, conveniently expressed by anharmonicity constants X-ij and vibrati on-rotation coupling constants alpha (r). Transition dipole moments were ca lculated for various stretching vibrational transitions.