  The infrared spectra of the weakly-bound dimers OCS-HCCCCH, in the region of
the nu1 fundamental band of OCS (2050 cm-1), and N2O-HCCCCH, in the region of
the nu1 fundamental band of N2O (2200 cm-1), were observed in a pulsed
supersonic slit jet expansion probed with tunable diode/QCL lasers. Both
OCS-HCCCCH and N2O-HCCCCH were found to have planar structure with side-by-side
monomer units having nearly parallel axes. These bands have hybrid rotational
structure which allows for estimates of the orientation of OCS and N2O in the
plane of their respective dimers. Analogous bands for OCS-DCCCCD and N2O-DCCCCD
were also observed and found to be consistent with the normal isotopologues.
Various levels of ab initio calculations were performed to find stationary
points on the potential energy surface, optimized structures and interaction
energies. Four stable geometries were found for OCS-HCCCCH and three for
N2O-HCCCCH. The rotational parameters at CCSD(T*)-F12c level of theory give
results in very good agreement with those obtained from the observed spectra.
In both dimers, the experimental structure corresponds to the lowest energy
isomer.
