The photon-driven chemistry of biacetyl (CH3COCOCH3) on Ag(111) has be
en studied using temperature-programmed desorption, Auger electron spe
ctroscopy, and time-of-flight mass spectrometry. Irradiation of both m
onolayer and multilayer biacetyl with 193 nm photons results in the pr
ompt ejection of CH3 radicals that exhibit bimodal translational tempe
ratures of 2700 +/- 100 and 290 +/- 20 K. Irradiation of multilayer bi
acetyl with 193 nm also leads to ejection of CO with translational tem
peratures of 1170 +/- 40 and 140 +/- 10 K, ketene (CH2CO) with transla
tional temperatures of 1000 +/- 60 K, and acetyl-containing fragments
with translational temperatures of 320 +/- 20 K. Indicative of the eje
ction of all reaction products from the surface during irradiation, po
stirradiation TPD shows loss of parent only, and C-(a) and O-(a) are a
bsent from the surface after irradiation and subsequent heating to 700
K. The cross section for total loss of 1 ML biacetyl is 2.0 +/- 0.3 x
10(-21) cm(+2) at 193 nm. Studies using 248 nm radiation, as well as
radiation from a Hg are lamp, were also undertaken.