Photodissociation dynamics of H2S at 121.6 nm and a determination of the potential energy function of SH( A 2Σ+)

We present the results of a joint experimental and theoretical investigation of the reaction dynamics of the HϩHD→DϩH 2 chemical reaction. The experiment was performed using a crossed molecular beam apparatus that employed the Rydberg-atom time-of-flight detection scheme for the product D atom. The photolysis of a HI precursor molecule produced a beam source of hot H atoms, which, when crossed with a cold HD beam, yielded two well-defined center-of-mass collision energies, E C ϭ0.498 and 1.200 eV. The resolution of the experiment was sufficient to allow the measurement of the rovibrationally state-resolved differential cross section from the ground state of the HD reagent. The reaction was modeled theoretically using a converged coupled channel scattering calculation employing the BKMP2 potential energy surface: The S matrix was computed on a grid of 56 energies in the range E C ϭ0.245-1.551 eV. It is found that the experimental and theoretical state-to-state differential cross sections are in quantitative agreement at the two experimental energies. The geometric phase, which was not included in the calculation, is apparently not required at the energies considered. The spin statistics for the two identical protons is observed to have a dramatic effect on the rotational distribution of H 2 products, giving rise to a saw-toothed distribution with odd-jЈϾeven-jЈ. The differential cross section for several of the product states exhibited a dramatic forward peak that may be the signature of trapped quantum states near the saddle point. A detailed analysis of the reaction attributes is presented based on the energy dependence of the computed S matrix.

Section: Experimental Methodsmentioning

confidence: 99%

A fully state- and angle-resolved study of the H+HD→D+H2 reaction: Comparison of a molecular beam experiment to ab initio quantum reaction dynamics

Chao

Harich

Dai

et al. 2002

“…Photodissociation of the CH 3 radical was studied at 212.5 nm using the H atom Rydberg ''tagging'' time-of-flight ͑TOF͒ technique, which was developed in the early 1990s by Welge and co-workers. 18 Detailed descriptions of this technique as used for studying molecular photodissociation can be found in Ref. 19.…”

Section: Methodsmentioning

confidence: 99%

Photodissociation dynamics of the methyl radical at 212.5 nm: Effect of parent internal excitation

Jiang

Qin

et al. 2004

Photodissociation dynamics of the CH 3 radical at 212.5 nm has been investigated using the H atom Rydberg tagging time-of-flight method with a pure CH 3 radical source generated by the photolysis of CH 3 I at 266 nm. Time-of-flight spectra of the H atom products from the photolysis of both cold and hot methyl radicals have been measured at different photolysis polarizations. Experimental results indicate that the photodissociation of the methyl radical in its ground vibrational state at 212.5 nm excitation occurs on a very fast time scale in comparison with its rotational period, indicating the CH 3 dissociation at 212.5 nm occurs on the excited 3s Rydberg state surface. Experimental evidence also shows that the photodissociation of the methyl radical in the 2 ϭ1 state of the umbrella mode at 212.5 nm excitation is characteristically different from that in the ground vibrational state.

“…Details of the experimental setup used in this work have been described previously. [15][16][17][18] Briefly, the H atom products in the photolysis region from the photodissociation of C 4 H 2 in the molecular beam are excited from the ground state to a high Rydberg state via a two-step excitation. The first excitation step was made by the 121.6 nm coherent light generated using the difference four wave mixing (DFWM) of 212.5 nm and 845 nm in a Kr cell in which two photons of 212.5 nm are in resonance with a Kr 4p-5p[1/2,0] transition.…”

Section: Experimental Methodsmentioning

confidence: 99%

Photodissociation dynamics of C4H2 at 164.41 nm: Competitive dissociation pathways

Zhang

et al. 2013

Photodissociation dynamics of C 4 H 2 at 164.41 nm through the Rydberg state R( 1 u ) have been studied using the high-resolution H atom Rydberg tagging technique. Experimental evidences show that two different predissociation pathways exist to form the ground C 4 H (X 2 + ) and electronically excited C 4 H (A 2 ) products: the former has statistical and isotropic translational energy distribution through internal conversion (IC) to the ground state, while the latter has non-statistical and anisotropic translational energy distribution through IC to the excited repulsive state. The vibrational progressions of C 4 H (A 2 ) products have also been observed and assigned.