Abstract

Small and medium-sized ketones are of interest due to their rich chemistry and involvement in practical combustion mechanisms. Further, the primary products of their dissociation, such as ethyl radicals and carbon monoxide in the present case, are themselves important combustion species. The photochemistry of ketones has been extensively investigated both by classical photochemical techniques, and more recently by methods that provide detailed information about the dissociation process and the disposition of energy in the fragments.¹ Acetone is the simplest ketone and serves as an excellent model for extending these studies to higher ketones. Recently, a number of investigations of acetone photodissociation have been carried out using pulsed UV radiation at 193 nm from an excimer laser. The next higher symmetrical analogue of acetone is 3-pentanone (diethylketone), and its photochemistry has also been investigated using classical techniques.² No investigations of 3-pentanone photolysis at shorter wavelengths or attempts to determine energy disposal among the fragments have been reported. A comparison of the photodissociation dynamics with those of the smaller ketone acetone should be illuminating. With this goal in mind, we have examined the photodissociation of diethylketone using our time-resolved FTIR apparatus, a commercial interferometer combined with a CAMAC-transient-digitizer-based data acquisition and storage system.³ One hundred interferograms were collected at 1-µs intervals; the laser was fired at the twentieth interval. The signal-to-noise ratio was further enhanced by combining our data into nonoverlapping 5 µs time bins before transformation.

© 1995 Optical Society of America