On class numbers of quadratic extensions¶over function fields

We consider class numbers of quadratic extensions over a fixed function field. We will show that there exist infinitely many quadratic extensions which have class numbers not being divisible by 3 and satisfy prescribed ramification conditions. Received: 24 October 1997 / Revised version: 26 February 1998     

Structure comparison between Th2Zn17-type and TbCu7-type Sm–Fe intermetallic compounds and their nitrides by means of 57Fe-Mössbauer spectroscopy

Samarium–iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th₂Zn₁₇-type and a TbCu₇-type structure, respectively. Structure comparison between these types was investigated for Sm–Fe intermetallic compounds and their nitrides by ⁵⁷Fe-Mössbauer spectroscopy.     

Annealing behavior of a void network in amorphous silicon

A void network in a-Si films prepared by vacuum deposition was studied. A close relationship in annealing behavior has been observed between the changes in surface area of voids and in the ESR signal strength.     

Magnetic field dip and the lifetime of the spherical tensor element of the density matrix in a He-Ne laser

The magnetic field dips (MFD) of the 0.633 and 1.15 μm lines of a He-Ne laser are investigated. It is found that the widths of the MFD signals are not determined by a single upper or lower laser state. Thus, there is some ambiguity in the interpretation of the MFD measurement for the determination of the lifetime, which is difficult to resolve theoretically or experimentally. The effect of pressure on MFD is also discussed, with emphasis on excitation-transfer collisions between the excited and ground states of neon atoms.     

Time-resolved total internal reflection fluorescence spectroscopy of polymer films

Using total internal reflection, the possibility of a subnanosecond fluorescence spectroscopy for elucidating photophysical and photochemical processes of polymer surface is demonstrated. The thickness which can be studied under the present experimental conditions is of the order of 0.01 μm.