Note: a laser-flash photolysis and laser-induced fluorescence detection technique for measuring total HO2 reactivity in ambient air

A novel instrument for measuring total HO2 reactivity in the troposphere was successfully developed using a laser-flash photolysis and laser-induced fluorescence detection technique. Validation and testing were conducted through kinetic measurements of the reaction of HO2 radicals with NO2, and the results were found to be in good agreement with recent recommended values. The limit of detection (LOD) for HO2 loss rate measurement is achieved to be 0.024 s(-1) (3σ) with 60 times decay integrations. An observation of ambient air was carried out in a suburb of Tokyo to test the practical use of the developed instrument and un-expected rapid HO2 loss rate has been observed.

Anomalous dressing of Dirac fermions in the topological surface state of Bi2Se3, Bi2Te3, and Cu-doped Bi2Se3

Quasiparticle dynamics on the topological surface state of Bi(2(3), Bi(2)Te(3), and superconducting Cu(x)Bi(2)Se(3) are studied by 7 eV laser-based angle resolved photoemission spectroscopy. We find strong mode couplings in the Dirac-cone surface states at energies of ~3 and ~15-20 meV associated with an exceptionally large coupling constant λ of ~3, which is one of the strongest ever reported for any material. This result is compatible with the recent observation of a strong Kohn anomaly in the surface phonon dispersion of Bi(2)Se(3), but it appears that the theoretically proposed "spin-plasmon" excitations realized in helical metals are also playing an important role. Intriguingly, the ~3 meV mode coupling is found to be enhanced in the superconducting state of Cu(x)Bi(2)Se(3).

Anomalous doping variation of the nodal low-energy feature of superconducting (Bi,Pb)2(Sr,La)2CuO(6+δ) crystals revealed by laser-based angle-resolved photoemission spectroscopy

The nodal band dispersion in (Bi,Pb)(2)(Sr,La)(2)CuO(6+δ) (Bi2201) is investigated over a wide range of doping by using 7-eV laser-based angle-resolved photoemission spectroscopy. We find that the low-energy band renormalization ("kink"), recently discovered in Bi(2)Sr(2)CaCu(2)O(8+δ) (Bi2212), also occurs in Bi2201, but at a binding energy around half that in Bi2212. Surprisingly, the coupling energy dramatically increases with a decrease of carrier concentration, showing a sharp enhancement across the optimal doping. These properties (material and doping dependence of the coupling energy) demonstrate the significant correlation among the mode coupling, the energy gap close to the node, and the strong electron correlation. Our results suggest forward scattering arising from the interplay between the electrons and in-plane polarized acoustic phonon branch as the origin of the low-energy renormalization.