THE CORRELATED PRODUCT STATE DISTRIBUTION OF KETENE PHOTODISSOCIATIONAT 308 NM

The correlated product state distribution for ketene photodissociation (CH2CO-->CH2+CO) at 308 nm has been measured by using quantum-state-s pecific metastable time-of-flight (TOF) spectroscopy. This distributio n is a matrix whose elements are the probability that if CO is produce d in the dissociation with quantum-state \n(CO)], CH2 will be produced with quantum-state \n(CH2)]. It was found that ketene photodissociati on yields CH2 in three resolved states; the (1)A(1) 1(000), and (1)A(1 )(010) states of CH2 are the major channels, while the B-3(1) State is a minor channel. In addition to this scalar distribution, the vector correlations between the recoil velocity and the angular momentum of t he CO fragment (v . j correlation), expressed by the beta(0)(0)(22) bi polar moment, have also been obtained as a function of the kinetic ene rgy release of the photoreaction. The correlated product state distrib ution was found not to follow the predictions of phase space theory, s uggesting that dynamic hindrances exist in the photoreaction that have not been previously observed. A phase space theory calculation with r estricted impact parameter values was also performed and compared to e xperiment. The impact parameter restricted phase space theory more acc urately reproduced all of the correlated product state information obt ained in this work as well as previous uncorrelated product state dist ributions for CH2 and CO. Both the ranges and the values of the allowe d impact parameters obtained from these restricted calculations increa se as the rotational energy of CO increases. Also, the values of the a llowed impact parameters for (1)A(1)(010) CH2 are larger than for (1)A (1)(000) CH2. This strongly suggests that C-C-O bending modes are hind ered at the transition state and therefore play an important role in t he photodissociation. (C) 1996 American Institute of Physics.