STRAIN DEPENDENCE OF THE VIBRATIONAL-MODES OF A DIACETYLENE CRYSTAL

In the reported experiments, resonance Raman spectroscopy has been used to measure the strain dependence of four high-frequency vibrational modes in a single crystal of toluene sulfonate diacetylene polymer. The 0. 62- mu m thick crystal was stretched elastically to 4% strain before fracture occurred. This was equivalent to an ultimate tensile strength of 2. 0 multiplied by 10**9N m** minus **2. The strain dependence of the vibrational modes has been interpreted using a simple point mass and anharmonic spring constant model. A Fermi resonance was observed for two vibrational modes which are degenerate at 2. 1% strain and a 1464 cm** minus **1 frequency.