Development of techniques that make use of synchrotron radiation (SR) and a soft x-ray monochromator enables us to investigate core-level photoexcitation and photoionization of gaseous molecules. With the linear polarization of intense soft x-rays from SR, one can observe angle-resolved fragments which help in selecting the molecular alignment or orientation at photoabsorption, since most of the fragmentation processes following the core-level photoexcitation and photoionization occur very fast. Moreover, one can combine the selection of molecular orientation or alignment with a coincidence measurement technique to perform novel measurements of the molecular core-level processes. Here, we introduce three measurement systems that we have developed: first, an angle-resolved photoion yield measurement, second, a vibrationally resolved photoelectron-photoion coincidence measurement, and third, a coincidence velocity map measurement. These measurement systems are explained along with individual applications as follows, the fragmentation dynamics of the Renner-Teller effect in the C1s → π* state of CO2 molecules, the shape resonance of vibrationally resolved core-level photoelectron angular distribution from fixed-in-space CO molecules, and the recoil frame photoelectron angular distributions of C1s electrons for C2H2 molecules with and without interference of photoelectron waves.
A genuine organic coexisting system of magnetism and conductivity has been realized. For this purpose, organic donor molecules carrying stable radicals in a cross-π-conjugated manner, so called “Spin-Polarized Donors”, have been developed. Among them, ESBN, consisting of a benzo-annulated selenium-containing TTF skeleton and a nitronylnitroxide moiety, was synthesized and its ionradical salt, (ESBN)2ClO4, was obtained by the electrochemical oxidation of ESBN. The interaction between conduction electrons in the mixed-valence π-staking column of donor moieties and localized spins in the radical moieties in this salt was confirmed by the appearance of giant negative magnetoresistance (–70% at 2 K, 9 T). The spin-dependent electron transport in this system is derived from the intramolecular magnetic coupling by means of orthogonality of molecular orbitals.
This article reviews recent advances in computer games. It is explained that methods famous in computational chemistry have enhanced the performance of Go and shogi programs. A history of the grand challenge in computer science that aims to defeat human experts in games is briefly summarized.
Laser spectroscopic study has been carried out for host-guest encapsulation complexes formed in supersonic jets and electrospray ionization cold 22 ion trap. The examined hosts include benzene-substituted 18-crown-6-ethers and calixarene, and for the guest species rare gas atoms, neutral molecules and alkali metal cations have been chosen. Various laser spectroscopic methods are applied: for the neutral complexes the electronic spectra are observed by laser-induced fluorescence (LIF), mass-selected resonance enhanced multiphoton ionization (REMPI) and ultraviolet-ultraviolet hole-burning (UV-UV HB) spectroscopy. The vibrational spectra are observed by infrared-ultraviolet double resonance (IR-UV DR) and fragment detected infrared photodissociation (IRPD) spectroscopy. For the ionic complexes, ultraviolet photodissociation (UVPD) and IR-UV DR spectroscopy has been applied. The obtained results are analyzed by density functional theory and first principles electronic structure calculations. We discuss how the host molecule changes its conformation or which conformer is preferred for forming stable encapsulation complex as well as the key interactions, leading to the molecular recognition.
Principles of organic photovoltaics such as p-i-n junction concept, nanostructure design, and bandgap science for organic semiconductors are surveyed. Details of the invention of p-i-n junction in the history of organic photovoltaics are described. Research targets based on molecular science, which assist the development of organic photovoltaics, are proposed.
Antihydrogen, the opposite number of hydrogen, is the simplest antimatter, and stable in vacuum, which guarantees a long observation time for high precision spectroscopy. This review discusses a short history of antimatter followed by the motivation of the cold antihydrogen research, and then a couple of latest results, which open a new era of antihydrogen research enabling high precision spectroscopy for the first time. A comparison of the spectroscopic properties of antihydrogen with those of hydrogen constitutes a stringent test of the CPT symmetry, the most fundamental law of physics. One of the important achievements of cold antihydrogen study in the last couple of years is the trapping of antihydrogen atoms in an octupole magnetic bottle. Considering the bottle depth, the trapped antihydrogen atoms were really cold, less than 0.5K in their temperature. High precision laser spectroscopy of 1S-2S transition is foreseen once antihydrogen atoms can be laser-cooled. The other milestone development was a successful synthesis of antihydrogen atoms in a so-called cusp trap, where an anti-Helmholtz coil configuration is adopted. The cusp trap enables extraction of antihydrogen atoms in a field-free region as an intensified spin-polarized beam,which realizes high resolution microwave spectroscopy of ground state hyperfine transitions.
Different intermolecular interactions in solutions produce various “mixing states”, such as ideal mixing, formation of clusters with the same component or another component and phase separation. The structure of a solution has been expressed by the radial distribution function from the microscopic standpoint. As a complementation for solution chemistry, a mesoscopic viewpoint is necessary to clarify the mixing state of a solution, because the mixing state is expressed in terms of fluctuations of the molecular distribution which are actualized in the mesoscopic special scale. The theoretical concept on fluctuations for solutions was first presented by Bhatia and Thornton. We established experimental methodologies to elucidate structures of solutions with fluctuations. For various solutions and mixtures in supercritical states, we obtained their density fluctuations, concentration fluctuations, particle-number fluctuations of individual components, and the Kirkwood-Buff parameters. As two examples, we present the mixing states of acetonitrile aqueous solutions and the ones of an n-pentane-water mixture in the supercritical state.
A growth model of nanocarbons including fullerenes and carbon nanotubes is described on the basis of experimental results accumulated in our research group during the last 25 years. In this model, a special attention is placed on the relationship between the initial condition for the carbon clustering process and the selectivity in pentagon and hexagon network formation which leads to clarify the reason why a sort of selection rule was found in the structures of nanocarbons. On the basis of the present model, a new method for preparing the carbon nanotube with a single chirality is proposed.
Although gold (Au) in bulk is almost inert as a catalyst, it turns to be active for many reactions when deposited as nanoparticles (NPs) and clusters on base metal oxides. They are characterized by three features; active at low temperatures, enhanced by water, and uniquely selective. Over supported Au NPs CO adsorbs on the Au surfaces and O2 is activated at the perimeter interfaces around Au NPs. Both the two adsorbates react with each other at the perimeter interfaces. Gold clusters are expected to exhibit unique selectivity through the precise control of the number of atoms and the selection of appropriate support materials.