RESEARCH

 In addition to the great impact on the progress of quantum mechanics at its early stage, Stern-Gerlachexperiment, the study on interaction of atoms with magnetic field, has lead to the invention of nuclear magnetic resonance and magnetic resonance imaging. As this classical example, the investigation of particle-field interaction has been beneficial to whole science area. Main topic of our group is experimental research and application of molecular interaction with various fields, such as nonresonant laser field and its combination with static electric field. The force imparted by the molecule-field interaction is exploited to spatially separate stereoisomers and their quantum states. Beside, in collaboration with Fritz Haber Institute in Berlin, grazing incidence atom optics is investigated.

 Molecule Optics: As a optical prism separates photons as their refractive indices, a molecule prism, which is made of nonresonant laser pulse, can separate molecules of different molecule refractive indices. As a proof-of-principle experiment, we separated benzene and NO molecules according to their polarizability to mass ratio, which is related to the molecule refractive index. Without laser both molecules are detected at the same position. However, with the molecule prism formed by the laser field, they were separated with a choromatographic resolution of 0.90. This can be beginning of a new separation method. In the future, the separation of different rotational states or streoisomers will be pursued.

Grazing Incidence Atom Optics
A: Artist’s view of quantum reflection of a helium dimer at the attractive van der Waals surface potential.
B: The He-He interaction potential (black) and the calculated probability function of 4He2 (red) as a function of internuclear separation.
C: Schematic of the experimental setup. (Fritz Haber Institute of Max Planck Society)

A 확대: The brown-yellow surface indicates He2-surface interaction potential. The scale of height above the surface is logarithmic. The well depth of the typical He2-surface potential is an order of 10 meV, which is 100 thousand times larger than the binding energy of the dimer, 0.1 meV. If the dimer enters this well, the acceleration due to the potential well smashes it into the surface and dissociates it. Quantum reflection, however, allows helium dimer to be reflected from a solid surface before it reaches a potential well as in this artistic view.

B 확대: Theoreticians calculated He-He pair potential and molecular wave function. Their calculation shows peculiar properties of helium dimer. In this graph, x-axis is logarithmic scale of internuclear separation and y- axis is potential energy.. The thick red curve represents the molecular wave function of the helium dimer. The extremely small binding energy allows the molecular wave function in the range of the larger internuclear separation than the classical turning point. The diameter of the dimer, given by the mean internuclear separation, is estimated to be 5.2 nm. Therefore, the helium dimer is a totally quantum mechanical system.