Bum Suk Zhao

Molecular lens applied to benzene and carbon disulfide molecular beams

A molecular lens of the nonresonant dipole force formed by focusing a nanosecond IR laser pulse has been applied to benzene and CS2 molecular beams. Using the velocity map imaging technique for molecular ray tracing, characteristic molecular lens parameters including the focal length (f ), minimum beam width (W), and distance to the minimum beam width position (D) were determined. The laser intensity dependence of the observed lens parameters was in good agreement with theoretical predictions. W was independent of the laser peak intensity (I0), whereas f and D varied linearly with 1/I0. The differences in lens parameters between the molecular species were well correlated with the polarizability per mass values of the molecules. A high chromatographic resolution of Rs=0.84 was achieved between the images of benzene molecular beams undeflected and deflected by the lens. The possibilities for a new type of chromatography are discussed.

Separation of a benzene and nitric oxide mixture by a molecule prism

In molecule optics, a matter wave of molecules is manipulated by a molecule-optical component made out of external, typically radiative, fields. The molecule-optical index of refraction, n, for a nonresonant IR laser pulse focused onto a molecular beam can be obtained from the energy conservation and wave properties of molecules. Experimentally measured values of n for benzene and nitric oxide agreed well with the calculated values. Since n depends on the properties of molecules as well as those of the laser field, a molecule prism composed of the focused nonresonant laser field can separate a multi-component molecular beam into several components according to their molecule-optical refractive indices n. We obtained a chromatographic resolution of 0.62 for the spatial separation of a mixture beam of benzene and nitric oxide using a focused Nd:YAG laser pulse as a molecule prism.

Quantum Reflection of He2 Several Nanometers Above a Grating Surface

The helium molecule can interact at large distances with the evanescent repulsion potential of the surface. Quantum reflection allows an atom or molecule to be reflected from a solid before it reaches the region where it would encounter the repulsive potential of the surface. We observed nondestructive scattering of the helium dimer (He2), which has a binding energy of 10−7 electron volt, from a solid reflection grating. We scattered a beam containing the dimer as well as atomic helium and larger clusters, but could differentiate the dimer by its diffraction angle. Helium dimers are quantum reflected tens of nanometers above the surface, where the surface-induced forces are too weak to dissociate the fragile bond.

Quantum reflection of helium atom beams from a microstructured grating

We observe high-resolution diffraction patterns of a thermal-energy helium atom beam reflected from a microstructured surface grating at grazing incidence. The grating consists of

Coherent Reflection of He Atom Beams from Rough Surfaces at Grazing Incidence

10\text{\ensuremath{-}}\ensuremath{\mu}\mathrm{m}

Emerging Beam Resonances in Atom Diffraction from a Reflection Grating

-wide Cr strips patterned on a quartz substrate and has a periodicity of

Non-destructive quantum reflection of helium dimers and trimers from a plane ruled grating

20\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}

Emerging beam effects in out-of-plane grating diffraction of he atom beams

. Fully resolved diffraction peaks up to the seventh order are observed at grazing angles up to

Focusing a helium atom beam using a quantum-reflection mirror

20\phantom{\rule{0.3em}{0ex}}\mathrm{mrad}

Slow Molecules Produced by Photodissociation

. With changes in de Broglie wavelength or grazing angle the relative diffraction intensities show significant variations which shed light on the nature of the atom-surface interaction potential. The observations are explained in terms of quantum reflection at the long-range attractive Casimir\char21{}van der Waals potential.