Volume 133, Issue 13, 07 October 2010
Index of content:
: Two-photon dissociation via the electronic state" title="Quantum state-selected photodissociation dynamics of : Two-photon dissociation via the electronic state" />
The photodissociation dynamics of via the state by two-photon excitation has been investigated using the H atom Rydberg tagging time-of-flight technique. The rotational resolved action spectrum of the transition band has been measured. The line widths show a pronounced dependence on the parent rotational excitation in the state. The quantum state resolved OH product translational energy distributions and angular distributions have also been obtained. By carefully simulating these distributions, quantum state distributions of the OH product as well as the state-resolved angular anisotropy parameters were determined. The experimental results confirm the variation of two competitive predissociation pathways. A heterogeneous predissociation channel is mediated by rotational coupling to the state associated with the -axis , and a homogeneous pathway arises from purely electronic coupling to the state. We have also obtained the branching ratios of the and products, and related these to the and pathways. The branching ratios display a strong dependence.
Communication: Experimental and theoretical investigations of the effects of the reactant bending excitations in the reaction133(2010); http://dx.doi.org/10.1063/1.3490795View Description Hide Description
The effects of the reactant bending excitations in the reaction are investigated by crossed molecular beam experiments and quasiclassical trajectory(QCT) calculations using a high-quality ab initio potential energy surface. The collision energy dependence of the cross sections of the reactions for the correlated product pairs and is obtained. Both experiment and theory show that the bending excitation activates the reaction at low and begins to inactivate at higher . The experimental excitation functions display surprising peak features, especially for the channels, indicating reactive resonances (quantum effects), which cannot be captured by quasiclassical calculations. The reactant state-specific QCT calculations predict that the bending mode excitation is the most efficient to drive the reaction and the and modes enhance the DF and HF channels, respectively.
Communication: The application of the global isomorphism to the study of liquid-vapor equilibrium in two and three-dimensional Lennard-Jones fluids133(2010); http://dx.doi.org/10.1063/1.3499857View Description Hide Description
We analyze the interrelation between the coexistence curve of the Lennard-Jones fluid and the Ising model in two and three dimensions within the global isomorphism approach proposed earlier [V. L. Kulinskii, J. Phys. Chem. B114, 2852 (2010)]. In case of two dimensions, we use the exact Onsager result to construct the binodal of the corresponding Lennard-Jones fluid and compare it with the results of the simulations. In the three-dimensional case, we use available numerical results for the Ising model for the corresponding mapping. The possibility to observe the singularity of the binodal diameter is discussed.
133(2010); http://dx.doi.org/10.1063/1.3475517View Description Hide Description
We report a joint experimental and theoretical study that directly tests the quality of the potential energy surfaces used to calculate energy changing cross sections of water in collision with helium and molecular hydrogen, at conditions relevant for astrophysics. Fully state-to-state differential cross sections are measured for and collisions at 429 and collision energy, respectively. We compare these differential cross sections with theoretical ones for derived from state-of-the-art potential energy surfaces [P. Valiron et al., J. Chem. Phys.129, 134306 (2008)] and quantum scattering calculations. This detailed comparison forms a stringent test of the validity of astrophysics calculations for energy changing rates in water. The agreement between theory and experiment is striking for most of the state-to-state differential cross sections measured.