In situ Fourier transform infrared spectroscopy is used to characterize the plasma chemistry of pulsed 1,3-butadiene (H2C=CHCH=CH2) discharges subject to varying percentages of the duty cycle in a gaseous electronics conference cell. Variations in densities associated with the major observed spectral bands are closely examined as a function of duty cycle. The possible dissociation mechanisms responsible for all observed vibrations are investigated. For example, the data show that about 44% of CH2 stretching vibrations during continuous wave biasing are due to free CH2 daughter species, while only bound CH2 are observed during pulsing of the discharge. This indicates that only the pi bond of the C=C bond is cleaved during pulsed mode operation, with the sigma being cleaved during cw biasing. (c) 2006 American Vacuum Society.