On the equilibrium structures of the complexes H2C3H+ • Ar and c-C3H3+ • Ar: Results of explicitly correlated coupled cluster calculations

Explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x = a, b) level [T. B. Adler et al., J. Chem. Phys. 127, 221106 (2007)] has been employed in a study of the potential energy surfaces for the complexes H2C3H+ center dot Ar and c-C3H3+ center dot Ar. For the former complex, a pronounced minimum with C-s symmetry was found (D-e approximate to 780 cm(-1)), well below the local "H-bound" minimum with C-2 nu symmetry (D-e approximate to 585 cm(-1)). The absorption at 3238 cm(-1) found in the recent infrared photodissociation spectra [A. M. Ricks et al., J. Chem. Phys. 132, 051101 (2010)] is, thus, interpreted as an essentially free acetylenic CH stretching vibration of the propargyl cation. A global minimum of C-s symmetry was also obtained for c-C3H3+ (D-e approximate to 580 cm(-1)), but the energy difference with respect to the local C-2 nu minimum is only 54 cm(-1). (C) 2011 American Institute of Physics. [doi:10.1063/1.3525466]