System for coincidence measurements of the ions desorbed and projectiles scattered from noble gas solid surfaces by slow multiply charged ion impacts

We have developed a new experimental apparatus for performing coincidence measurements of the ions desorbed and projectiles scattered from the surfaces of noble gas solids by slow multiply charged ion impacts at grazing incidence angles. This simultaneously measures the desorbed ions' flight times and the scattered projectiles' charge states. We also conduct experiments on 6 keV Ar⁶⁺ impacts onto a solid Ne surface using the device.     

Light-harvesting and energy-transfer system based on self-assembling perylene diimide-appended hexaazatriphenylene

[reaction: see text]. Six perylene diimide-appended hexaazatriphenylene, HAT-PDI(6), was self-assembled in both solution and film state to form a highly stabilized dimer aggregate, in which an efficient energy transfer occurs from the hexaazatriphenylene core to the perylene-diimide moiety.     

g-Factor Measurements of Rotational States in 84,86Zr

The g-factors of the positive parity yrast rotational states in ^84,86Zr have been precisely measured using a TMF-IMPAD method. The measured g factors indicate the proton alignment followed by neutron alignment in the g _9/2 high-j shell for ⁸⁴Zr and the neutron alignment followed by proton alignment for ⁸⁶Zr. The present results also reveal the structure transition at N=46 for Zr isotopes. This revised version was published online in September 2006 with corrections to the Cover Date.     

Hyperfine Interactions of 8Li in Ferromagnetic Single Crystal Fe

The hyperfine interactions of ⁸Li implanted in single crystal Fe have been studied using the β-NMR technique. One kind of hyperfine field B _hf was found. Since no dipolar field was observed, ⁸Li nuclei are suggested to sit in substitutional sites. The B _hf and the spin-lattice relaxation time T ₁ were observed as functions of temperature. The experimental B _hf and T ₁ were compared with the theoretical predictions from the first principles KKR-band-structure calculations. While predicted B _hf for the substitutional site is consistent with the experiment, predicted T ₁ cannot reproduce the experiment well. This revised version was published online in September 2006 with corrections to the Cover Date.     

Hyperfine Interactions of 12B in CaB6

The hyperfine interactions of short-lived β-emitter ¹²B implanted into a CaB₆ crystal have been studied by means of the β-NMR technique. An electric quadrupole splitting has been observed at room temperature from which an electric field gradient of q=−(1.34±0.05)×10²¹ V/m² was determined. From the present result, it was found that the ¹²B nuclei are mainly implanted in the substitutional boron site. This revised version was published online in September 2006 with corrections to the Cover Date.     

Beta and gamma decays of J π = 1+, 24mAl state

A β-γ spectroscopy of the J ^π , 426 keV isomeric state of ²⁴Al (^24m Al) has been carried out by using a ²⁴Al secondary beam with high purity and high isomeric ratio. From the absolute γ-ray and β-particle intensities observed in the decay of the isomeric state, the branching ratio R _B of the isomeric γ decay from ^24m Al to the J ^π = 4⁺, ground state of ²⁴Al have been derived. The obtained R _B value of 69.6(7)% is much smaller than the previously accepted value of 82.5(30)%. The precise half-life for the isomer decay, T _1/2 ^m = 130.9(13) ms, has been also determined in this experiment. Accordingly, the M3 γ-decay strength B(M3) of the ^24m Al decay becomes smaller and the total β-decay branching ratio becomes larger. In particular, the β-decay branching ratio to the ground state of ²⁴Mg becomes 24.3(9)%, which is 2.4 times larger than the previous value of 10.1(28)%. By combining the branching ratio and the half-life, the Gamow-Teller (GT) transition strength B(GT) of 0.0194(7) is deduced for the GT transition from ^24m Al to the J ^π = 0⁺, ground state of ²⁴Mg. This value is in good agreement with the values derived from charge-exchange reactions.     

Spin control and structure of weak nucleon currents in A= 8, 12, 20 and 41

The β-ray angular distributions from purely spin aligned ¹²B and ¹²N were precisely remeasured using a further refined spin-manipulation technique. We determined the amount of a g-parity violating induced tensor form factor in a weak axial vector current as 2M f_T/f_A= +0.22 ± 0.05\ (stat.) ± 0.15\ (syst.) ± 0.05\ (theor.). The result is consistent with the theoretical prediction in the framework of which induced tensor form factor is proportional to u- and d-quark mass difference. To study the g-parity violation in weak nucleon current systematically, we have started to measure the alignment correlation terms of ⁸Li, ⁸B, ²⁰F and ⁴¹Sc. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spin control of 12B and 12N and the axial charge from their β-ray spin-alignment correlations

The spin manipulation technique by use of the β-NMR is further refined, based on the recent thorough studies of hyperfine interactions of ¹²B and ¹²N in Mg. By using this technique, the alignment correlation terms in the β-ray angular distribution of the A = 12 system are precisely measured, so that the axial charge is singled out to be y = 4.66 ± 0.06 (stat.) ± 0.13 (syst.) which shows clear mesonic enhancement over the impulse value. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hyperfine Interactions of Short-Lived β Emitters in Pd

The Knight shifts K and the spin-lattice relaxation time T ₁ for the short-lived β-emitters ¹²B and ¹²N implanted into Pd have been measured by means of the β-NMR method. The results show that K depends on temperature. The obtained values of experimental K were compared with theoretical values derived with the KKR method.