Abstract:

Photodissociation dynamics of n-C3H7I and i-C3H7I at 266 nm were investigated using an ion imaging technique combined with resonance enhanced multiphoton ionization (REMPI). Information on energy disposal and a nonadiabatic transition between the dissociative electronic states involved in the photodissociation of both molecules were analyzed and compared. The fraction of internal energy in the I channel is greater than that in the I* channel for both molecules. As the alkyl group becomes more branched the energy distribution of the atom fragments (I and I*) becomes obviously wider suggesting that the alkyl radical at the α-carbon atomhas more complicated models of the ro-vibration models. On the other hand, the relative oscillator strengths of these molecules that were pumped using 266 nm photons show a small difference in the 3Q0←X transition. The probability of yielding an I* fragment decreases markedly from 0.72 for n-C3H7I to 0.46 for i-C3H7I. This is attributed to the greater contribution of the bending modes for I and I* during the photodissociation of i-C3H7I than that of n-C3H7I leading to an enhancement of the nonadiabatic transition between the 3Q0 and 1Q1 states. Additionally, the 3Q0←X transition is not a completely parallel transition for both molecules and the angle between the transition dipole moment and the bond axis is estimated to be about 15° for n-C3H7I and 18° for i-C3H7I, respectively.

Key words: Photodissociation dynamics, n-C3H7I, i-C3H7I, Ion imaging