Modeling ionic unimolecular dissociations from a temperature controlled TPEPICO study on 1-C4H9I ions

We report on the development of a new temperature controlled inlet system for the study of gas phase unimolecular reaction dynamics using threshold photoelectron photoion coincidence (TPEPICO) spectroscopy. Temperatures in the range of 220-400 K can be achieved, with a deviation of less than 5 K over the course of a 48 h experiment. Iodine loss from energy selected 1-butyl iodide (1-C4H9I) ions was studied at four temperatures, 220, 275, 298 and 400 K. The fractional ion abundances, in the form of breakdown diagrams are presented. Particular attention is paid to the slopes of the molecular and daughter ion abundances in crossover region of the breakdown curve since they are governed solely by the internal energy distribution, P(E), of the neutral precursor. P(E) is a function of both the temperature and vibrational frequencies of the neutral precursor. A detailed discussion regarding the transposition of the neutral thermal energy distribution to the ionic manifold is presented. From the four experimental measurements, the E0 for the production of the 2-C4H9+ ion was determined to be 9.738 ± 0.015 eV.