Using Ion-velocity Map Imaging Technique to Study Photodissociation of 2-Bromopentane

Photodissociation dynamics of carbonyl sulfide (OCS) in the deep ultraviolet region is investigated using a time-sliced ion velocity map imaging technique. The measured total kinetic energy release spectra from the photodissociation of OCS at ∼210 nm shows three dissociation channels to the fragment S(D), corresponding to low, medium, and high kinetic energy release (E), respectively. The high E channel is found to be a new dissociation channel opening with photolysis wavelength at ∼210 nm. Based on the a(p) polarization parameters as well as the anisotropy parameters β determined from the images of S(D), the dissociation of OCS to S(D) + CO at 210 nm is concluded to involve a direct vertical excitation of the triplet c(2A) state from the ground state, followed by processes as: the low E component arises from a non-adiabatic transition from the repulsive A(2A) state to the electronic ground state X(1A); the medium E component arises from a simultaneous excitation to two repulsive excited states; and the high E component arises from the intersystem crossing from the triplet c(2A) state to the repulsive A(2A) state. The present study shows that, due to the strong spin-orbit coupling between the triplet c(2A) state and the repulsive A(2A) state, a direct excitation to c(2A) significantly contributes to the photodissociation dynamics of OCS in the deep-UV region.

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Photodissociation Dynamics of OCS at 217 nm

Bai

Liang

Zhou

et al. 2017

Chinese Journal of Chemical Physics

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The S(1 D 2)+CO(X 1 Σ +) product channel from photodissociation of OCS at 217 nm has been measured using the DC slice velocity map imaging (VMI) technique in combination with resonance enhanced multiphoton ionization (REMPI). Two different REMPI intermediate states (1 F 3 and 1 P 1) and several pump-probe laser polarization geometries are used to detect the angular momentum polarization of the photofragmented S(1 D 2). The molecularframe polarization parameters, as well as the laboratory-frame anisotropy parameters, for individual rotational states of co-fragment CO, are determined using two different full quantum theories. The measured total kinetic energy release spectrum from photodissociation of OCS indicates two dissociation channels, corresponding to the fast and slow recoiling velocities of S(1 D 2), respectively. The slow channel is concluded to originate from an initial photoexcitation to the A(1 A ′) state, followed by a non-adiabatic transition to the ground state. The fast channel is found to follow a coherent excitation to A(1 A ′) and B(1 A ′′) states, where contributions of the two states are almost equal at 217 nm. The determined alignment and anisotropy parameters further indicate that the slow channel follows an incoherent excitation, while the fast channel follows a coherent excitation to A(1 A ′) and B(1 A ′′) states with a phase difference of π/2.

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Using Ion-velocity Map Imaging Technique to Study Photodissociation of 2-Bromopentane

Cited by 4 publications

References 22 publications

DC slice ion imaging of the ultraviolet photodissociation of 2-bromohexane

DC slice ion imaging of the ultraviolet photodissociation of 2-bromohexane

Photodissociation dynamics of OCS at ∼210 nm: The role of c(23A″) state

Photodissociation Dynamics of OCS at 217 nm

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