Observation of the matrix effect due to the electron transfer in laser ablation plasma

We investigate the so-called “matrix effect” on the relative intensities of ions in mixed solutions of alkali salts by using femtosecond laser ablation time-of-flight mass spectrometry (fsLA-TOFMS). For the 1:1 mixed solution of sodium and potassium salts, the intensity ratio of cations (Na⁺/K⁺) decreases as the total concentration increases. From the measurement for the mixed solution of lithium, sodium, potassium, rubidium, and cesium solutions, we find out significant dependence of each ion intensity on the total concentration. The results suggest that the electron transfer from neutral atoms to cations coexistent in the ablation plasma affects the relative ion intensities observed with TOFMS when the total ion concentration is high.     

MD simulation study of the sputtering process by high-energy gas cluster impact

We performed molecular dynamics (MD) simulations to study the characteristic sputtering process with large cluster ion impact. The statistical properties of incident Ar and sputtered Si atoms were examined using 100 different MD simulations with Ar₁₀₀₀ cluster impacting on a Si(0 0 1) target at a total acceleration energy of 50 keV. The results show that the kinetic energy distribution of Ar atoms after impact obeys the high-temperature Boltzmann distribution due to thermalization through high-density multiple collisions on the target. On the other hand, the kinetic energy distribution of sputtered target atoms demonstrates a hybrid model of thermalization and collision-cascade desorption processes.     

Laser spectroscopy of exotic RI atoms in superfluid helium—OROCHI experiment

We have been developing a new laser spectroscopic technique “OROCHI,” which is based on the combination of superfluid helium as a stopper of radioactive isotope (RI) beam and in-situ laser spectroscopy of RI atoms, for determining spins and moments of exotic RIs. By using this unique technique, it is feasible to measure nuclear spins and electromagnetic moments of extremely low yield RI (estimated as less than 1 pps). Recently, we have demonstrated that nuclear spins and moments are obtained from Zeeman and hyperfine splittings of stable Rb isotopes measured using this OROCHI technique. Details of this laser spectroscopy method in He II “OROCHI” and the summary of our development are presented.     

Synthesis and Mechanical Properties of Polypropylene-based Polymer Hybrids via Controlled Radical Polymerization

Isotactic polypropylene-based graft copolymers linking poly(methyl methacrylate), poly(n-butyl acrylate) and polystyrene were successfully synthesized by a controlled radical polymerization with isotactic polypropylene (iPP) macroinitiator. The hydroxylated iPP, prepared by propylene/10-undecen-1-ol copolymerization with a metallocene/methyl-aluminoxane/triisobutylaluminum catalyst system, was treated with 2-bromoisobutyryl bromide to produce a Br-group containing iPP (PP-g-Br). The resulting PP-g-Br could initiate controlled radical polymerization of methyl methacrylate, n-butyl acrylate and styrene by using a copper catalyst system, leading to a variety of iPP-based graft copolymers with a different content of the corresponding polar segment. These graft copolymers demonstrated unique mechanical properties dependent upon the kind and content of the grafted polar segment.