The infrared absorption spectra of (HCCH)2 and (DCCD)2

Abstract
The infrared absorption bands of acetylene dimers have been investigated with long path low temperature Fourier transform infrared spectroscopy. Five bands were found, three of (HCCH)2 and two of (DCCD)2. Four of these bands can be assigned as coupled monomer modes. Normal mode analysis based on a theoretical intermolecular potential confirms these assignments. One band shows evidence of fast vibrational predissociation, and a symmetry based argument is made to support the claim that the predissociation fragments are rotationally excited.