High resolution IR spectroscopy of acetylene-furan in ultracold helium nanodroplets.

We have measured the IR spectrum of the acetylene-furan complex in ultracold helium nanodroplets in the region of the nu(3) CH(asym)-stretch vibration of the acetylene (between 3240 and 3300 cm(-1)). We have observed eight bands that can be attributed to acetylene-furan complexes. Two of these bands are assigned to two different isomers of the 1:1 acetylene-furan complex. The vibrational band at 3267.4 cm(-1) is assigned to the CH(asym)-stretch vibration of the dimer structure with the C-H of the acetylene being attached to the pi-system of the furan. The peak at 3272.1 cm(-1) is assigned to the CH(asym)-stretch vibration of the dimer structure with the C-H of the acetylene being attached to the oxygen atom of the furan. These assignments are confirmed by additional measurements of the spectrum of the (13)C-acetylene-furan complex.