THE GEOMETRIC STRUCTURE AND STABILITY OF THE NO-DOT-CH4 CATIONIC COMPLEX(CENTER)

Ab initio calculations have been performed, mainly at the MP2 level of theory, using a variety of basis sets, to elucidate the structure of the NO+. CH, cationic complex. The complex has an equilibrium geometry of C-s symmetry, in which the NO+ moiety eclipses a C-H bond of the m ethane molecule. The geometry is compared to those of related complexe s. Harmonic vibrational frequencies are also calculated, together with the interaction energy and some thermodynamic quantities for the comp lex formation, employing a number of the theoretical methods. In parti cular, the interaction energy was calculated at the CCSD(T) level of t heory. The implications of these results on the resonance-enhanced mul tiphoton ionization (REMPI) spectroscopy of the NO . CH4 complex are b riefly discussed. (C) 1997 Elsevier Science B.V.