The Explicit Simplified Interface Method for compressible multicomponent flows

This paper concerns the numerical approximation of the Euler equations for multicomponent flows. A numerical method is proposed to reduce spurious oscillations that classically occur around material interfaces. It is based on the "Explicit Simplified Interface Method" (ESIM), previously developed in the linear case of acoustics with stationary interfaces (2001, J. Comput. Phys. 168, pp.~227-248). This technique amounts to a higher order extension of the "Ghost Fluid Method" introduced in Euler multicomponent flows (1999, J. Comput. Phys. 152, pp. 457-492). The ESIM is coupled to sophisticated shock-capturing schemes for time-marching, and to level-sets for tracking material interfaces. Jump conditions satisfied by the exact solution and by its spatial derivative are incorporated in numerical schemes, ensuring a subcell resolution of material interfaces inside the meshing. Numerical experiments show the efficiency of the method for rich-structured flows.Comment: to be published in SIAM Journal of Scientific Computing (2005

Distinction of Nuclear Spin States with the Scanning Tunneling Microscope

We demonstrate rotational excitation spectroscopy with the scanning tunneling microscope for physisorbed hydrogen and its isotopes hydrogen-deuterid and deuterium. The observed excitation energies are very close to the gas phase values and show the expected scaling with moment of inertia. Since these energies are characteristic for the molecular nuclear spin states we are able to identify the para and ortho species of hydrogen and deuterium, respectively. We thereby demonstrate nuclear spin sensitivity with unprecedented spatial resolution

Rotational Excitation Spectroscopy with the STM through Molecular Resonances

We investigate the rotational properties of molecular hydrogen and its isotopes physisorbed on the surfaces of graphene and hexagonal boron nitride ($h$-BN), grown on Ni(111), Ru(0001), and Rh(111), using rotational excitation spectroscopy (RES) with the scanning tunneling microscope. The rotational thresholds are in good agreement with $\Delta J=2$ transitions of freely spinning para-H$_2$ and ortho-D$_2$ molecules. The line shape variations in RES for H$_2$ among the different surfaces can be traced back and naturally explained by a resonance mediated tunneling mechanism. RES data for H$_2$/$h$-BN/Rh(111) suggests a local intrinsic gating on this surface due to lateral variations in the surface potential. An RES inspection of H$_2$, HD, and D$_2$ mixtures finally points to a multi molecule excitation, since either of the three $J=0\rightarrow2$ rotational transitions are simultaneously present, irrespective of where the spectra were recorded in the mixed monolayer