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[en] This paper reports on superconducting coupling nature at grain boundaries in Bi₂Sr₂CaCu₂O_x glass-ceramics which consist mainly of the low-T_c phase first examined by measuring superconducting properties and temperature or ac field dependence of ac complex susceptibility. It was found from the ac loss peaks that superconducting coupling at grain boundaries was basically characterized by three types of weak links. The weak-link behaviors at grain boundaries depended strongly on cooling conditions after annealing and annealing time and temperature. Particularly, it was found that the weak links at grain boundaries were improved by prolonged annealing at 840 degrees C. The furnace-cooled glass-ceramics obtained by annealing at 820 degrees or 840 degrees C for about 200 h exhibited a critical transport current density (77 K, zero magnetic field) of about 200 A/cm²

[en] An abrupt change in the spectral width of optogalvanic (OG) signals of Kr atomic lines has been observed at a distance from the cathode wall where the signal itself changes its sign, by using a hollow cathode lamp whose cathode has its both ends open. The width is broader near the cathode wall with its magnitude varying by discharge current while the narrower width which is obtained on passing the laser beam in the central region of cathode cylinder is independent of the current. It is suggested that a well-defined region, where the particles of larger cross section of collisions with Kr atom are confined, is present in front of the cathode wall. (orig.)

[en] Doppler-Free Lamb dip and intermodulated spectra of He₂ b ³Pi/sub g/--f ³Δ/sub u/ transition have been observed by the technique of optogalvanic spectroscopy. The analysis of the triplet splittings of rotational lines yielded the values of spin-orbit (A), spin--spin (lambda/sub zeta/ and lambda/sub perpendicular//sub perpendicular/) and spin-orbit (γ) coupling constants of A/sub Pi/ = -6.75₃ +- 0.26, lambda/sub zeta/ = 3.06₉ +- 0.37, lambda/sub perpendicular//sub perpendicular/ = -4.48₀ +- 0.03, γ = -0.00₉ +- 0.02 GHz for the b ³Pi/sub g/ state, and A/sub Δ/ = -0.07₃ +- 0.10, lambda/sub zeta/ = 027₆ +- 0.27, and γ = 0.01₆ +- 0.03 GHz for the f ³Δ/sub u/ state. The Λ-type doubling in the b ³Pi/sub g/ state was found negligible. The derived values for the b ³Pi/sub g/ state are compared with those for the H₂ c ³Pi/sub u/ state which has the optical electron in the same 2pπ orbital as He₂ b ³Pi/sub g/ state, and the departure of the electron configuration in the He₂ b ⁴Pi/sub g/ state from the united atom orbital (UAO) is discussed

[en] He 3 ¹/sup ,/³D--2 ³P lines have been investigated by optogalvanic spectroscopy in the hollow cathode discharge of He to reveal the presence of the 3 ¹D₂--2 ³P₂ component which is predicted at 0.0764 cm^-1 above the 3 ¹D₂--2 ³P₁ line appearing at 17 018.137 +- 0.004 cm^-1. The assignment of the latter has also been experimentally established by the present study through the use of optogalvanic double resonance methods. The spin-orbit interaction of the 3 ¹D₂ level with the 3 ³D₂ level is responsible for the appearance of the 3 ¹D₂--2 ³P₂ line. The relaxation processes among the 3 ¹D, 3 ³D, and 2 ³P levels have also been briefly discussed on the basis of the observations of mysterious dips on the double resonance signals and of a broad background signal on Doppler-free intermodulation spectrum

[en] The Ag-coated superconducting Bi₂Sr₂CaCu₂O_x glass-ceramic fibers were successfully prepared. The glass fibers with a length of 50 cm, a width of 100--200 μm, and a thickness of about 20 μm were first drawn from glass plates with a thickness of 1 mm and then silver pastes were coated on the smooth surface of glass fibers. The Ag-coated glass fibers were converted into superconductors after annealing at temperatures of 820--860 degree C. The main crystalline phase in the glass-ceramic fibers was the superconducting low T_c phase. The Ag-coated glass-ceramic fibers obtained by annealing at 840 degree C for 5 h in air exhibited superconductivity with a T_c(zero)=70 K and a critical current density (60 K, zero magnetic field) of more than 40 A/cm²