Fast and exceptionally slow vibrational energy transfer in acetylene and phenylacetylene in solution

Abstract
The excitation of the CH‐stretching mode (ν3) of C2H2 in CCl4 leads to fast population (2). The long lifetime of ν2 is due to the absence of anharmonic interaction to neighboring states (symmetry forbidden). The corresponding CC‐stretching mode of C6H5–C2H has a lifetime of 15 ps. The phenyl group relaxes the symmetry restrictions and introduces new decay channels.