Enhanced action spectra of combination bands of acetylene via vibrationally mediated photodissociation and fragment ionization Academic Article uri icon


  • Abstract Vibrational excitation combined with promotion of acetylene molecules to the excited electronic trans-bent states A (1 A u)/B (1 B u) and fragment ionization are used to generate action spectra. Rovibrational states of acetylene in the 15480–15723 cm− 1 region are accessed with high sensitivity and photodissociated by 243.135 nm photons that also tag the H fragments. Transition intensities of the combination bands that involve high stretch and low bend excitation (1410 0 2 0) and (2031 1 0 0) are 0.5±0.1 and 0.7±0.1, respectively, times that of the fourth overtone of the C–H stretch (2030 0 0 0). These intensities are more than an order of magnitude higher than in the absorption spectrum and result from better Franck–Condon overlap between combination bands and the upper bent-electronic states.

publication date

  • January 1, 1998