Observation of intermediate bands feeding the positive-parity yrast band in 155Gd

High-spin states of ¹⁵⁵Gd were populated by using the ¹⁵⁴Sm(α,3nγ)¹⁵⁵Gd reaction at E _α= 33 MeV. γ-γ coincidence, E _γ singles, excitation function, and the DCO ratios were measured. we have identified three intermediate bands with ΔI= 2 feeding the positive yrast band. The bands are interpreted as such candidate bands that are mixed with the negative-parity ground state band. This observation can provide a plausible explanation for unusually large population of the positive-parity yrast band observed in a recent Coulomb excitation. Received: 2 November 1999     

Quantum dynamics of a generalized Coleman-Hepp model

Studies on a generalized Coleman-Hepp model are done on the basis of a spin coherent state representation and a transformation property of the model Hamiltonian. Namely, transforming the original model Hamiltonian into a simpler form, we can determine time evolution of the whole system by successive applications of rotation operators in a spinor space. Dynamics of detector spins as well as that of an incident particle are fully discussed. Explicit numerical evaluations are also performed. Relevance of our solution to a generalized Cini model is also briefly mentioned. Received 24 August 1999     

Orthogonal acoustical factors of a sound field in a bamboo forest.

To investigate the acoustical quality of a sound field in a bamboo forest, acoustical measurements were conducted to obtain orthogonal acoustical factors of the sound field. These results are compared with previous results for a sound field in an ordinary forest [H. Sakai, S. Sato, and Y. Ando, J. Acoust. Soc. Am. 104, 1491-1497 (1998)]. The IACC, which is defined as a maximum value of the normalized interaural cross-correlation function between signals at the ears, was 0.07 (4 kHz) and 0.16 (2 kHz) at positions 20 and 40 m from the source, respectively. These values are much better than those in the previously investigated forest. The measured subsequent reverberation time Tsub was up to 1.5 s in the frequency range above 1 kHz at the position 40 m from the source. For certain music sources with higher frequency components, therefore, sound fields in a bamboo forest have excellent acoustic properties.     

Real-to-imaginary ratio of the pp forward elastic scattering amplitude in the momentum range between 180 and 590 MeV/c

The real-to-imaginary ratio of the $\text{p}\text{p}$ forward elastic scattering amplitude has been measured at the LEAR facility of CERN by the Coulomb-nuclear interference method at seven beam momenta between 181 and 590 MeV/c. The ratio is positive at 590 MeV/c, becomes negative below 500 MeV/c, reaches a minimum at 260 MeV/c and then crosses zero again at about 230 MeV/c.     

Magnetic properties of some gadolinium—Cobalt intermetallic compounds

Crystallographic and magnetic properties of the single crystals having the compositions of GdCo₃, Gd₂Co₇, GdCo₅, Gd_2.2Co_16.6 and Gd₂Co₁₇ were studied in order to contribute to the investigation of the magnetic anisotropy in the Gd–Co system. The single crystal used were prepared by means of the Bridgman method using BN-coated alumina crucibles.The room-temperature magnetocrystalline anisotropy constants K₁ of GdCo₃, Gd₂Co₇, GdCo₅, Gd_2.2Co_16.6 and Gd₂Co₁₇ are determined as 8.1 × 10⁶, 1.3 × 10⁷, 4.1 × 10⁷, 3.0 × 10⁶ and -2.7 × 10⁶ erg/cm³, respectively. it is also found that the magnetocrystalline anisotropy of Gd–Co phases in the stable region of the Th₂Zn₁₇-type structure changes very sensitively from negative to positive as the ratio Gd/Co increases above the stoichiometric ratio of 2/17.     

Exciton migration in a fluctuating medium I

A statistical mechanical theory of exciton migration in a fluctuating environment is developed with the use of the time-convolutionless equation formalism. This gives a satisfactory result when the stochastic perturbations acting on excitons are assumed to be Gaussian.Our theory is valid for any timescale and is applicable to the case of off-diagonal randomness as well as the diagonal randomness. For the Gaussian-Markoffian process, a basic equation can be solved analytically to give optical absorption spectra and the density of states. These quantities show systematic variations when certain characteristic parameters are changed.     

Thermal variation of attenuation for optical fibers

Thermal variation of attenuation for multi-component and high-silica glass fibers has been measured at 0.63 μm wavelength in a temperature range from 20°C to 600°C. The multicomponent glass fibers have shown no increase in loss below 400°C, whereas the high-silica glass fibers have shown a drastic, exponential increase in loss with increasing temperature. The observed change of attenuation has been explained on the basis of the shift of the ultra-violet absorption band calculated from temperature change of refractive index. The increase in optical loss, calculated from the obtained data of refractive index and dispersion parameters at each temperature, shows good agreement with the observed increase in loss.