Xirong Chen

Reaction dynamics of

Abstract The reaction dynamics of O(3P) and H2(v=1) have been studied experimentally by laser induced fluorescence (LIF) detection of the radical OH(X2Π, v=0,1). The reactant H2(v=1) is prepared by stimulated Raman pumping (SRP). The Λ-doublet states are found to be selectively populated in the vibrational ground state, with the X2Π(A′)/X2Π(A″) ratio ranging from 1.4 at low J to 2.3 in the high J limit. OH( X 2 Π, v=1 ) was observed, and the OH(v″=0)/OH(v″=1) ratio was estimated to be ⩾25. Possible mechanisms are discussed.

SO(X 3Σ−) production from the 193 nm laser photolysis of thionyl fluoride

The vibrational and rotational state distribution and the primary quantum yield of the SO(X 3Σ−) fragment following the laser photolysis of F2SO at 193 nm have been measured by using laser-induced fluorescence spectroscopy on the SO(B 3Σ−-X 3Σ−) transition. Molecular elimination of F2 is the only energetically allowed channel to produce the SO fragment. The quantum yield measurement, Φ193 nmSO(X)=0.06±0.01, suggests that other photochemical channels, e.g. FSO+F, must be operative as well.

Internal energy distributions of the SO(X)3Σ−) product from the O(3P) + OCS reaction

Abstract The SO(X 3 Σ − ) product vibrational and rotational state distributions following the title reaction have been studied by laser induced fluorescence on the (B 3 Σ − -X 3 Σ − ) transition. The O( 3 P) atom was generated by 351 nm photolysis of NO 2 . The SO(X 3 Σ − ) product is highly vibrationally excited and the vibrational state distribution is inverted at v ″=5 with detectable population up to v ″=9. The observed vibrational state distribution has been modelled effectively by a Franck-Condon/Golden Rule treatment. The nascent rotational state distribution of v ″=4 and 6 can be characterized by rotational temperatures, T R =2288±357 K and T R =2227±297 K, respectively. The rotational state populations are nearly equilibrated with the ambient gas within 10 hard sphere collisions. A surprisal analysis reveals that the observed rotational state distribution is colder than would be predicted on the basis of a purely statistical energy disposal model. The observed SO(X 3 Σ − ) internal energy accounts for ≈ 34% of the total energy available to products. The non-statistical energy disposal results are consistent with a direct S atom abstraction mechanism.

Photodissociation studies of cyclic sulfoxides

The gas phase photodissociation of the cyclic sulfoxides, (CH2)nSO (n equals 2, 3, 4), has been studied following 193 and 248 nm photolysis. The nascent vibrational state distribution of the SO(X3(Sigma) -) photofragment following photolysis of each cyclic sulfoxide contains detailed information about the photochemical mechanisms. The SO vibrational state distributions have been measured by laser induced fluorescence spectroscopy on the (B3(Sigma) - -- X3(Sigma) -) transition, after 193 and 248 nm photodissociation of each cyclic sulfoxide. The observed vibrational state distributions are compared with physical models to help reveal the fragmentation mechanisms.