The hopping motion of the self-trapped exciton in NaCl

The decay kinetics and the yield of the π luminescence from the lowest triplet state of the self-trapped exciton have been studied in NaCl containing Li⁺ ions. It is found that the π luminescence band which is observed at 6K is replaced by a luminescence band peaked at 3.34 eV above 77K. The 3.34 eV luminescence band is ascribed to the recombination of the relaxed exciton trapped by a Li⁺ ion, (V_ke)_Li. The decay of the π luminescence induced by an electron pulse and the time change of the luminescence from (V_ke)_Li are explained in terms of the characteristic equation of the diffusion-limited reaction of the lowest triplet self-trapped excitons with the Li⁺ ions. From the analysis of the dependence of the decay rate of the π luminescence on temperature and on the Li⁺ concentration, we found the diffusion constant D of the lowest triplet self-trapped exciton in NaCl to be given by with $\text{D}{}_0\text{= 2.13 × 10}{}^{\mathrm{?3}}\text{cm}{}^2\text{s}$ and E₀ = 0.13 eV. The present result can be regarded as the first clear experimental evidence for the hopping diffusion of the self-trapped exciton in alkali halides. The obtained values of E_a and D₀ are discussed using the small polaron theory. The effect of the anharmonicity on the hopping of the self-trapped excitons is suggested to be significant.     

Two-loop double-pole counter lagrangian

On the basis of the background field method, extended one-loop counterterm formulae are derived, and a method to get the two-loop double-pole counter lagrangian is given. As an example, the double-pole divergences of ξ²X³ counterterms are obtained.     

Energy transfer due to excitons and holes under host-sensitization in KBr:I

Energy transfer due to excitons and holes to iodine ions in KBr:I crystals has been investigated. It is confirmed that, when the exciting photon energy is increased beyond the Γ-band edges of KBr, probability of the energy transfer due to exciton diffusion rapidly decreases with the complementary enhancement of that due to hole migration followed by electron capture.     

Polarization labelling spectroscopy of the A 1Σ+u band of Na2

A result of the polarization labelling spectroscopy of the A ¹Σ⁺_u band of sodium dimer for the high vibrational quantum number υ'>20 is reported. The frequency difference δv=v_obs-v_cal is found to decrease from 2 to -3 cm^-1 as the rotational levels (υ'=27?30), where v_cal is the calculated transition frequency using the Dunham coefficients of Demtröder and Stock for the X ¹Σ⁺_g band and of Kusch and Hessel for the A ¹Σ⁺_u band.     

Observation of the color-suppressed decay B( 0)-->D(0)pi(0)

We report the first observation of color-suppressed B( 0)-->D(0)pi(0), D(*0)pi(0), D0eta, and D0omega decays, and evidence for B( 0)-->D(*0)eta and D(*0)omega. The branching fractions are B(B( 0)-->D0pi(0)) = (3.1 +/- 0.4 +/- 0.5)x10(-4), B(B( 0) -->D(*0)pi(0)) = (2.7(+0.8+0.5)(-0.7-0.6))x10(-4), B(B( 0) --> D0eta) = (1.4(+0.5)(-0.4) +/- 0.3)x10(-4), B(B( 0) --> D0omega) = (1.8 +/- 0.5(+0.4)(-0.3))x10(-4), and we set 90% confidence level upper limits of B(B( 0) --> D(*0)eta)<4.6 x 10(-4) and B(B( 0)-->D(*0)omega)<7.9 x 10(-4). The analysis is based on a data sample of 21.3 fb(-1) collected at the Upsilon(4S) resonance by the Belle detector at the KEKB e(+)e(-) collider.     

Probability of statistical L-H transition in tokamaks

A statistical model for the bifurcation of the radial electric field Er is analyzed in view of describing L-H transitions of tokamak plasmas. Noise in microfluctuations is shown to lead to random changes of Er if a deterministic approach allows for more than one solution. The probability density function for and the ensemble average of Er are obtained. The L-to-H and the H-to-L transition probabilities are calculated, and the effective phase limit is derived. Because of the suppression of turbulence by shear in Er, the limit deviates from Maxwell's rule.     

Observation of B+/- -->omegaK+/- decay

We report the first observation of the charmless two-body mode B+/--->omegaK+/- decay, and a new measurement of the branching fraction for the B+/--->omegapi(+/-) decay. The measured branching fractions are B(B+/--->omegaK+/-)=(9.2(+2.6)(-2.3)+/-1.0)x10(-6) and B(B+/--->omegapi(+/-))=(4.2(+2.0)(-1.8)+/-0.5)x10(-6). We also measure the partial rate asymmetry of B+/--->omegaK+/- decays and obtain A(CP)=-0.21+/-0.28+/-0.03. The results are based on a data sample of 29.4 fb(-1) collected on the Upsilon(4S) resonance by the Belle detector at the KEKB e(+)e(-) collider.     

Composite optical waveguide composed of a tapered film of bromothymol blue evaporated onto a potassium ion-exchanged waveguide and its application as a guided wave absorption-based ammonia-gas sensor

For what is the first time to our knowledge, we have successfully evaporated a tapered film of bromothymol blue (BTB) onto a potassium ion-exchanged (PIE) waveguide to form a composite optical waveguide (COWG) for trace-ammonia detection. The BTB film has a high refractive index (1.69) and a smooth surface and is transparent to a 633-nm laser beam in air. In the COWG structure, the BTB film serves as a single-mode waveguide, and adiabatic transition of the TE(0) mode was realized between the BTB waveguide and the PIE waveguide with both BTB tapers. In the presence of ammonia, the BTB film changes color from yellow to blue, which causes absorption of the 633-nm guided wave. Our experimental results demonstrate that such a guided wave absorption-based ammonia-gas sensor is much more sensitive than one based on evanescent-wave absorption. A detection limit of part in 10(9) of ammonia has been realized for a BTB film-PIE glass COWG.