M. Hori

Reversible Control of Hydrogenation of a Single Molecule

Low-temperature scanning tunneling microscopy was used to selectively break the N-H bond of a methylaminocarbyne (CNHCH3) molecule on a Pt(111) surface at 4.7 kelvin, leaving the C-H bonds intact, to form an adsorbed methylisocyanide molecule (CNCH3). The methylisocyanide product was identified through comparison of its vibrational spectrum with that of directly adsorbed methylisocyanide as measured with inelastic electron tunneling spectroscopy. The CNHCH3 could be regenerated in situ by exposure to hydrogen at room temperature. The combination of tip-induced dehydrogenation with thermodynamically driven hydrogenation allows a completely reversible chemical cycle to be established at the single-molecule level in this system. By tailoring the pulse conditions, irreversible dissociation entailing cleavage of both the C-H and N-H bonds can also be demonstrated.

Hyperfine structure of the metastable p̄He+ atomcule revealed by a laser-induced (n, l) = (37, 35) → (38, 34) transition

Abstract A precise scan of the previously discovered laser-induced transition ( n, l ) = (37, 35) → (38, 34) in pHe + revealed a doublet structure with a separation of Δ ν HF = 1.70 ± 0.05 GHz. This new type of “hyperfine” splitting is ascribed to the interaction of the antiproton orbital angular momentum and the electron spin.

Laser resonance studies of the interactions of metastable antiprotonic helium atomcules p4He+ with surrounding H2 molecules

Abstract We have employed a laser resonance method to study the interactions of individual states of metastable antiprotonic atomcules p He + with surrounding H 2 molecules. We have found that the lifetimes of the ( n , 1) = (37,34) and (39,35) states are shortened by small admixtures of H 2 molecules in quite different ways; the observed quenching cross section for the upper (39,35) state in helium medium at 1 bar and 30 K is (2.4 ± 1.0) × 10 −15 cm 2 , a factor of 24 larger than that for the lower (37,34) state.

Self-Assembly of Meta-Aminobenzoate on Cu(110)

A variety of structures of meta-aminobenzoate molecules adsorbed on the Cu(110) surface have been characterized by scanning tunneling microscopy (STM) at a wide range of surface coverages, from a single molecule to saturated phases. At the start of molecular domain formation, individual molecules thermally diffuse to form chain structures via intermolecular hydrogen bonding. At higher surface coverages, there coexist three well-ordered phases, namely [Formula: see text] and chiral [Formula: see text] phases. The molecular orientation on the surface also varies with surface coverage. Flat-lying molecules are mainly observed at low surface coverage, while upright molecules start to appear as the surface becomes more highly covered. Our experimental findings and structural analysis are well supported by high-resolution STM images measured at 4.7 K and by molecular packing models with precise lattice parameters.

Interaction of antiprotonic helium atoms with H2 molecules

The interaction of antiprotonic helium atoms with surrounding H 2 molecules was studied microscopically using laser spectroscopy. The state-dependent quenching effects observed were employed to induce laser resonance transitions between normally metastable states.

Effect of Substituent Position on Molecular Assembly: Hydrogen-Bonded Arrangement of Aminobenzoates Adsorbed on Cu(110)

The growth and assembly of the aminobenzoate (NH2C6H4COO-) isomers, ortho-aminobenzoate (OAB), meta-aminobenzoate (MAB), and para-aminobenzoate (PAB), on Cu(110) have been investigated by low-temperature scanning tunneling microscopy (STM). In the submonolayer regions, OAB and PAB formed well-ordered islands, whereas MAB produced disordering when dosed at room temperature. We found that the growth of the OAB and PAB layers proceeds in a different manner. The OAB islands developed from the step site to the terrace, while the nucleation and growth of the PAB islands occurred at the terrace. An increase in the surface coverage resulted in further growth of the islands for the OAB and PAB layers, which ended with the formation of ordered monolayers with (4×3) and (3×4) superstructures, respectively. In contrast, MAB showed a complex self-assembly on the Cu(110) surface. Our STM study clearly demonstrates that the substituent position in the aminobenzoate affects not only the monolayer structure but also the growth process.

Laser spectroscopy of antiprotonic helium and stringent constraint on the antiproton charge and mass

a Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan b CERN, CH-1211, Geneva 23, Switzerland c Physik-Department, Technische Universit ̈ at München, D-85747 Garching, Germany d KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, Hungary e Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan f Institute for Particle and Nuclear Studies, KEK-Tanashi, Tokyo 188-8501, Japan g Institute of Physics, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan h Japan Society for Promotion of Science, Koji-machi, Chiyoda-ku, Tokyo 102-8471, Japan

Scanning Tunneling Microscopy and Inelastic Electron Tunneling Spectroscopy Studies of Methyl Isocyanide Adsorbed on Pt(111)

A low-temperature scanning tunneling microscope (STM) was used to investigate the adsorption state of a single methyl isocyanide (MeNC) molecule on the Pt(111) surface at 4.7 K. We found that MeNC was resolved as a round-shaped protrusion in the STM image. The STM image of paired MeNC is highly protruded in comparison with that of isolated MeNC due to the charge transfer from Pt to MeNC. Inelastic electron tunneling spectroscopy with the STM system (STM-IETS) was also employed in order to reveal the adsorption state of individual MeNC molecules on Pt(111). The STM-IETS spectrum of MeNC exhibits peaks at 8, 48 and 375 mV. Referring to the vibrational spectra reported previously, we assigned these peaks to the frustrated translation mode, PtC stretching mode and CH3 stretching mode, respectively. The absence of other vibrational modes could be due to a reduction of the elastic tunneling current.