| It is important theoretically and practically that the ketene photodissociationas a model system for unimolecular dissociation. Photodissociation dynamics ofketene following excitation at 208nm, 213nm and 218 nm have been investigatedusing the velocity map ion-imaging method. Both the angular distribution andtranslational energy distribution of the CO products at different rotational andvibrational states have been obtained. The results are as follows:1 No significant difference in the translational energy distributions for different CO rotational state products has been observed at 208nm and 213nm excitation wavelengths. The anisotropy parameterβis, however, noticeably different for different CO rotational state products at these two excitation wavelengths. For lower rotational states of the CO product, βis smaller than zero, while βis larger than zero for CO at higher rotational states. The observed rotational dependence of angular anisotropy is interpreted as the dynamical influence of a peculiar conical intersection between the 1B1 excited state and 1A2 excited state along the CS-I coordinate.2 The major photodissociation pathway of ketene following the excitation at 218 nm is the CH2 (a1A1) + CO(X1Σ+ ) channel, while the CH2 (b1B1) + CO(X1Σ+ ) channel and the CH2(X3B1) + CO(X1Σ+ ) channel are also likely present.Another important experimental work has been done by the author, which isthe experimental study of the quantum interference effect in collisional inducedrotational energy transfer of CO (A1Π, v=0 / e3Σ-, v=1)-HCl system. The presentwork reports our study on quantum interference effect in rotational energy transferwithin CO (A1Π, v=0 / e3Σ-, v=1) mixed states in collision with HCl. Theinterference phase angle θST obtained are 101°±3°and 110°±5°for ?J = ±1transition respectively from the initial J = 12 and 13 states. It is the first time thatthe interference phase angle is larger than 90°has been observed experimentally.
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