Photodissociation dynamics of 1-propanol and 2-propanol at 193.3 nm

193.3-nm photodissociation dynamics of jet-cooled 1-propanol and 2-propanol and their partially deuterated variants are examined by using the high-n Rydberg-atom time-of-flight technique. Isotope labeling studies show that O–H bond fission is the primary H-atom production channel in the ultraviolet photodissociation of both 1-propanol and 2-propanol. Center-of-mass (c.m.) product translational energy release of the RO–H dissociation channel is large, with 〈fT〉=0.78 for H+1-propoxy (n-propoxy) and 0.79 for H+2-propoxy (isoproxy). Maximum c.m. translational energy release yields an upper limit of the O–H bond dissociation energy: 433±2 kJ/mol in 1-propanol and 435±2 kJ/mol in 2-propanol. H-atom product angular distribution is anisotropic (with β≈−0.79 for 1-propanol and −0.77 for 2-propanol), suggesting an electronic transition moment perpendicular to the H–O–C plane and a short excited-state dissociation lifetime (less than a rotational period). Information about photodissociation dynamics and bond energies of the partially deuterated propanols are also obtained. The 193.3-nm photodissociation dynamics of 1-propanol and 2-propanol are nearly identical to each other and are similar to those of methanol and ethanol. This indicates a common RO–H dissociation mechanism: after the nO→σ*(O–H)/3s excitation localized on the H–O–C moiety, the H atom is ejected promptly in the H–O–C plane in a time scale shorter than a rotational period of the parent molecule, and it dissociates along the O–H coordinate on the repulsive excited-state potential-energy surface with a large translational energy release.