15min:

CHAKREE TANJAROON AND WOLFGANG JÄGER, Department of Chemistry, The University of Alberta, Edmonton, T6G 2G2 Canada.

The rotational spectra of three very weakly bound complexes, He₁-C₅H₅N, He₂-C₅H₅N, and H₂-C₅H₅N, have been studied using a pulsed molecular beam microwave spectroscopic method. Analysis of the rotational and ¹⁴N nuclear quadrupole coupling constants of these complexes shows that all three complexes possess the perpendicular geometric configuration. In this configuration, in the dimer, He and H₂ bind above the aromatic plan of C₅H₅N and are displaced by less than ten degrees away from the c-axis of the pyridine monomer, toward the nitrogen atom. In the trimer, the second helium atom preferentially binds below the aromatic plan of C₅H₅N, opposite of the first helium atom. An MP2 ab initio interaction potential between He and C₅H₅N has been generated and the theoretical results are consistent with those from the experiment. The spectra, molecular structures, quadrupole coupling parameters, and interaction potentials will be discussed.