Mass-Spectrometric Investigation of the Primary Processes in the Photodissociation of 1,3-Butadiene

The primary processes in the 1,3-butadiene photodissociation are investigated by direct detection of the fragments in a mass spectrometer at pressures of 10−4 mm Hg in the reaction chamber. With the special technique used here, collisions do not occur during the time between photon impact and primary-product detection. The resulting products of illumination with a light continuum between 2200 and 1800 Å, which is produced by a pulsed high-pressure argon flash lamp, are as follows: C3H3 + CH3; C4H5 + H; C2H4 + C2H2; C2H3 + C2H3; and to a small amount, also C4H4 + H2. The quantitative probabilities for these five dissociation modes are derived from the measured ion spectrum of the neutral photodissociation fragments that is produced in the ion chamber of the mass spectrometer by electron impact. Some results concerning the original excited state and fragment energies are discussed.