Kaoru Yamanouchi

Stainless steels are basic corrosion-resistant materials, but despite great efforts for over a century, they still suffer inevitably from environmental erosions by ubiquitous chemical reactions, resulting in typical corrosion rates at dozens of μm∙yr^-1. Here, we developed a strong-field laser passivation strategy to obtain super corrosion-resistant stainless steels through forming a hybrid µm-Fe₃O₄/Fe₂O₃/Cr₂O₃ passivation layer with unique bionic taro-leaf-like hierarchically heterogeneous Cassie-state micro/nanostructure morphologies. We observed up to 100,000-fold reduction in the corrosion rate of AISI 304 steel in saline, acidic as well as alkaline solutions. The ultralow corrosion rate can remain for >6500 hours. The generality was exemplified by exhibiting extreme anticorrosion enhancements of AISI 316, 420, 201, 430, and 2205 steels under the same conditions. This study reveals a new strategy for achieving super corrosion-resistant performance of stainless steels in various harsh environments.

We examine the ionization of NO2 in an ultrashort-pulsed near-IR intense laser field (790 nm, 100 fs, 8 × 1013 W/cm2) by recording the NO2+ yield as a function of time delay between a pump laser pulse, creating a rotational wave packet of NO2, and a probe laser pulse, ionizing NO2 to NO2+. We quantitatively interpret a periodic rotational revival structure accompanied by a fast oscillation with a period of 1.1 ps appearing in the time-delay dependence of the NO2+ yield by treating NO2 as a near-prolate top molecule. By numerical simulations of the time evolution of the rotational wave packet of NO2, we reveal that the ionization of NO2 is enhanced when the molecular b axis, corresponding to the C2 symmetry axis, is parallel to the laser polarization direction.

We determine the energies of hyperfine structure splitting of Kr + 83 and isotope shifts in the fine structure splitting of Kr + with precision of sub-MHz ( ∼ 10 − 5 c m − 1 ) by strong-field ultrahigh resolution Fourier-transform spectroscopy. From the splitting energies, we determine the hyperfine structure constants of Kr + 83 and the isotope shift parameters of Kr + . Based on the field shift parameters, we identify the deformation of the electron density distribution of the 4p orbital of Kr + originating from the relativistic effect.

We simulate the time-dependent rovibronic wave function of H 2 + in an intense, few-cycle 400 nm laser field using a time-dependent multiconfiguration method. By calculating the expectation value of the total angular momentum squared, the time-dependent expectation value of the internuclear distance, the induced dipole moment, and the probability of electron ejection, we show that rotational, vibrational and electronic excitation as well as ionization can be simulated. We compare the results obtained using the time-dependent multiconfiguration method with the results obtained using the standard two-state Born-Oppenheimer approximation and the close-coupling expansion. We find that the multiconfiguration results for a wave function constructed using 21 time-dependent orbitals are in good agreement with the close-coupling results, but that the two-state Born-Oppenheimer approximation leads to an underestimation of the induced dipole moment by a factor of two and an overestimation the expectation value of the total angular momentum squared by a factor of 2.3.

Upon melting, the molecules in a crystal explore numerous configurations, reflecting an increase in disorder. The molar entropy of disorder can be defined by Boltzmann’s formula Δ S _d = R ln( W _d ), where W _d is the increase in the number of microscopic states, so far inaccessible experimentally. We found that the Arrhenius frequency factor A of the electron diffraction signal decay provides W _d through an experimental equation A = A _INT W _d , where A _INT is an inelastic scattering cross section. The method connects Clausius and Boltzmann experimentally and supplements the Clausius approach, being applicable to a femtogram quantity of thermally unstable and biomolecular crystals. The data also showed that crystal disordering and crystallization of melt are reciprocal, both governed by the entropy change but manifesting in opposite directions.