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Femtosecond time-resolved phototfragment translational spectroscopy was used for examining the photodissociation dynamics of acetone S2 (n, 3s) Rydberg state excited at 195nm. Average total kinetic energy releases of 31 kJ/mol for the primary dissociation and 50 kJ/mol for the secondary dissociation at 120ps were observed by the three-body kinematic analyses of the methyl kinetic energy distributions (KEDs).

Femtosecond pump-probe mass-selected multiphoton ionization spectroscopy was used for examining the photodissociation dynamics of the acetone S2 (n, 3s) Rydberg state excited at 195 nm. The initially excited S2 state undergoes a relatively slow internal conversion (IC) to the highly vibrationally excited region of the S1 state upon photoexcitation of acetone at 195 nm.

A nonstatistical behavior is observed in the photodissociation of two acyl cyanide compounds. The analysis reveals that the excited-state dissociation rate does not decrease with molecular size as much as statistical as statistical rate theory predicts. This suggests that a nonergodic system in which the available vibrational energy does not redistribute statistically among all modes before the bond breakage occurs.

Quadrupole mass filter and vacuum-ultraviolet ionization are used for measuring the time-of-flight spectra of species at mass-to-charge ratios from the reaction of N + Si[H.sub.4] in crossed molecular beams. The results have shown that SiN[H.sub.2] ([X.sup.2][B.sub.2]) and HNSi ([X.sup.1][[SIGMA].sup.+]) are dominant among isomeric products in the reaction of N + Si[H.sub.4].

An affirmative observation of concerted braking of two chemical bonds in the photodissociation of dimethyl sulfoxide (DMSO) is reported. It is concluded that, upon excitation near 200 nm, DMSO decomposes into SO + 2C[H.sub.3] with a quantum yield of approximately 1.5 for the methyl products.