Differing reactivities in the predissociation of acetylene isotopomers pre-excited with three C-H stretching quanta Academic Article uri icon

abstract

  • Selective photolysis of a mixture of acetylene isotopomers prepared in rovibrational states lying in the energy window of the second overtone of CH stretches was performed. Tunable near infrared (NIR) photons prepared the isotopomers in initial states and ultraviolet photons both promoted them to the excited electronic trans -bent A ̃ 1 A u state and tagged the H(D) photofragments via (2+1) resonantly enhanced multiphoton ionization. Photoacoustic spectroscopy monitored the initial state preparation and action spectroscopy simultaneously tagged the H(D) photoproducts yield as a function of the wavelength of the exciting NIR laser. The measurements and analysis indicate differing dissociation efficacies in C 2 H 2 and C 2 HD revealing enhanced CH bond cleavage in the former and hindered CH(D) bond fission in the latter. The enhancement is a result of coincident resonances with the upper state leading to sharp structures in the photodissociation cross-section of C 2 H 2 .

publication date

  • January 1, 2002