Least Squares Fitting of Perturbed Vibrational Polyads Near the Isomerization Barrier in the S_1 State of C_2H_2 Conference Paper uri icon


  • The S_1 electronic state of acetylene has recently been shown to have two potential minima, corresponding to cis-and trans-bent structures. The trans-bent isomer is the more stable, with the cis-bent isomer lying about 2670 cm^{-1} higher; the barrier to isomerization lies roughly 5000 cm^{-1} above the trans zero-point level. The``isomerization coordinate''(along which the molecule moves to get from the trans minimum to the barrier) is a combination of the nu_3 (trans bending) and nu_6 (cis bending) vibrational normal coordinates, but the spectrum is very confused because the nu_6 vibration interacts strongly with the nu_4 (torsion) vibration through Coriolis and Darling-Dennison resonances. Since the nu_4 and nu_6 fundamental frequencies are almost equal, the bending vibrational structure consists of polyads. At low vibrational energies the polyads where these three vibrations are …

publication date

  • June 1, 2013