title: A full-dimensional quantum dynamical study of H2+H2 collisions: coupled-states versus close-coupling formulation.
abstract: Collision-induced energy transfer involving H2 molecules plays an important role in many areas of physics. Kinetic models often require a complete set of state-to-state rate coefficients for H2+H2 collisions in order to interpret results from spectroscopic observations or to make quantitative predictions. Recent progress in full-dimensional quantum dynamics using the numerically exact close-coupling (CC) formulation has provided good agreement with existing experimental data for low-lying states of H2 and increased the number of state-to-state cross sections that may be reliably determined over a broad range of energies. Nevertheless, there exist many possible initial states (e.g., states with high rotational excitation) that still remain elusive from a computational standpoint even at relatively low collision energies. In these cases, the coupled-states (CS) approximation offers an alternative full-dimensional formulation. We assess the accuracy of the CS approximation for H2+H2 collisions by comparison with benchmark results obtained using the CC formulation. The results are used to provide insight into the orientation effects of the various internal energy transfer mechanisms. A statistical CS approximation is also investigated and cross sections are reported for transitions which would otherwise be impractical to compute.
authors: Department of Physics, Pennsylvania State University, Berks Campus, Reading, Pennsylvania 19610-6009, USA.
authors: Alex
authors: A
authors: Bohr
authors: Department of Physics, Pennsylvania State University, Berks Campus, Reading, Pennsylvania 19610-6009, USA.
authors: Stephen
authors: S
authors: Paolini
authors: Department of Physics, Pennsylvania State University, Berks Campus, Reading, Pennsylvania 19610-6009, USA.
authors: Robert C
authors: RC
authors: Forrey
authors: Department of Chemistry, University of Nevada Las Vegas, Las Vegas, Nevada 89154, USA.
authors: N
authors: N
authors: Balakrishnan
authors: Department of Physics and Astronomy and the Center for Simulational Physics, University of Georgia, Athens, Georgia 30602, USA.
authors: P C
authors: PC
authors: Stancil