It is shown that for nonzero temperature, Hubbard's narrow-energy-band model is neither ferromagnetic nor antiferromagnetic in one and two dimensions.

The mean lifetime and $g$ factor of the 2.95-MeV $6^{+}$ state of ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ were measured to be $\tau =1.76\mathrm{}\pm 0.03$ nsec and $\mathrm{}\left|g\right|=1.37\mathrm{}\pm 0.03$, respectively. These results are in agreement with the shell-model assignment ${\left({f_{\frac{7}{2}}}^{-2\mathrm{}}\right)}_{\pi }$ plus a small amount of configuration mixing which accounts for the quenching of the magnetic moment from the Schmidt limit and the enhanced $E2\mathrm{}$ rate $B(E2;6^{+}\to 4^{+})=3.2\mathrm{}$ Weisskopf units.

Measurement of the spin-flip probability with a polarized proton beam leads to a straightforward determination of both polarization ($P$) and analyzing power ($A$) in inelastic scattering at analog resonances. Calculations including direct-reaction background indicate that $P-A$ is insensitive to precise values of background parameters but quite sensitive to the configuration assumed for the analog state.

The magnetic moment of the 1142-keV $8^{-}$ state of ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}$ was deduced from the known hyperfine splitting of the isomeric state in (${\mathrm{Hf}}_{0.1}$${\mathrm{Zr}}_{0.9}$)${\mathrm{Fe}}_2$ and the hyperfine field in this compound. This field $H_{\mathrm{hf}}=-200\mathrm{}\pm 20$ kOe was obtained from Mössbauer experiments with the 93.3-keV $\gamma$ rays of ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}$. The deduced result $\mu \left(8^{-}\right)=+(8.6\mathrm{}\pm 1.0){\mu }_N$ identifies the $8^{-}$ state as a virtually pure two-proton configuration.

We studied the $\gamma$ decays of the lowest $T=2\mathrm{}$ state of ${}_{}{}^{32}{}_{}{}^{}\mathrm{P}$ using the reaction ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}({}_{}{}^3{}_{}{}^{}\mathrm{He},p\gamma )$. By combining our results with ($n,\gamma$) data, the excitation energy of the $T=2\mathrm{}$ state is found to be 5.0729 ± 0.0015 MeV. The implications of our results are discussed with reference to the search for $T=2\mathrm{}$ states in proton-rich nuclei, the comparison of analogous Gamow-Teller and $M1\mathrm{}$ decays, and the search for an isotensor component of the electromagnetic field.

Components modulated in intensity at discrete radio frequencies have been detected in the light from several stars. The effect is believed to be due to time-dependent, very small-angle scattering of the starlight by enhanced electron density fluctuations in the ionosphere.

We describe the analysis of an extremely energetic air shower produced by a primary cosmic-ray particle of energy 4 × ${10}^{21}$ eV. The arrival direction of this cosmic ray is right ascension 20 h 14.5 min and declination 24°. The directions of 3C409 (radio source) and A P20 15 ± 28 (pulsar) are inside the uncertainty of the arrival direction. Information on muons and the total number of charged particles in this air shower indicates no drastic change of nuclear interactions from ${10}^{17}$ to ${10}^{21}$ eV.

Many rare neutron-rich isotopes in the range $16<~Z\lesssim 34$ can be synthesized from seed nuclei exposed to explosive carbon burning. This process, which involves no new astrophysical parameters, can solve most of the outstanding problems in the thermonuclear synthesis of elements in the range $Z\lesssim 34$.

We have studied the reaction $e^{-}+p\to e^{-}+p+{\pi }^0$ by detecting the final electron and proton in coincidence. The data cover the region of virtual photon mass squared from -0.19 to -1.4 Ge${\mathrm{V}}^2$, and virtual photoproduction center-of-mass energy and angle from 1.84 to 2.50 GeV and 0° to 35°, respectively.

We have identified the annihilation mode $\overline{p}p\to 2{\pi }^0$ for antiprotons stopping in liquid hydrogen at a rate which is 0.15 (±20%) times that reported for $\overline{p}p\to {\pi }^{+}{\pi }^{-}$. This indicates that about 40% of all annihilations into $2\pi$ take place from odd-orbital atomic $\overline{p}p$ states, in contrast to the usual assumption that annihilation from the $s$ state predominates.

We present the low-energy limit of the one-loop contribution to $\gamma +\gamma \to 3{\pi }^0$ and ${\pi }^{+}+{\pi }^{-}+{\pi }^0$ in a linear $\sigma$ model. In this model calculation we have the Adler-Schwinger anomaly and we do not have to set all pion momenta equal to zero. Our result maintains gauge invariance and both amplitudes vanish in contradiction to the previous result of Aviv, Hari Dass, and Sawyer.

It is argued that hydrogen atoms formed by charge-transfer reactions with Xe at 15-eV incoming proton energy could be spin polarized. A detailed numerical calculation of the charge-transfer probability and the spin-polarization fraction indicate that a spin polarization as large as 70% may occur while the charge-transfer probability is simultaneously 0.6.

Penning ionization is shown to be the dominant ionization mechanism in a low-current He-Cd dc discharge under certain conditions. Properties of a discharge of this type are discussed.

The spectrum of depolarized light scattered from monatomic fluids has been measured as a function of temperature and density over a range extending from the dilute-gas limit to densities as much as 50% above the normal liquid density. The low-density spectra exhibit the nearly exponential character reported earlier. Above ∼ 200 amagats the spectra broaden at progressively higher density and exhibit qualitative changes at extremely high densities. Additional spectral-shape changes occur for very high effective temperatures.

The current-driven collisional drift instability is observed in a double-ended $Q$-machine cesium plasma. The instability is of large amplitude and leads to significant density decrease at onset. The characteristics of the instability are in good agreement with a linearized two-fluid theory which includes electron heat flow and electron temperature oscillations.

Flute instabilities driven by unfavorable magnetic field curvature can be stabilized by a positive ambipolar potential which confines cold electrons electrostatically. This mechanism does not depend on line tying in the conventional sense. We derive stability criteria and discuss their relation to experimental observations.

The first conclusive evidence for a tunneling selection rule for single-crystal superconductors is presented. Using tunneling data for the (001) plane of gallium obtained in two different laboratories, we show that the zero transverse $k$-vector rule of Dowman, Mac-Vicar, and Waldram is superior to the usual group-velocity rule. The dominant tunnel direction in real space is the normal to the tunnel barrier and does not appear to be affected by barrier orientation or structure.

We present the first direct and conclusive evidence of bound exciton resonance in phonon Raman scattering from solids. The observed enhancement in the 1LO scattering cross section at the $I_1$ bound exciton in CdS is a factor of ∼ 30 for the sample with the highest impurity content. In contrast to 1LO, the 2LO scattering cross section shows no enhancement near bound excitons. An explanation of this behavior is suggested.

The time-dependent rate of energy transfer, $k\left(t\right)\mathrm{}$, found by observation of sensitized fluorescence from certain organic mixed crystals, is analyzed in terms of results for the exciton master equation. A variety of possible explanations of the anomalous time dependence of $k\left(t\right)\mathrm{}$ are shown to be inconsistent with these results. A model that includes host traps which can slowly transfer energy back to the host is shown to give a good quantitative fit to the experimental $k\left(t\right)\mathrm{}$.

Investigation of photoluminescence excitation spectra in GaAs proves that the capture of hot conduction-band electrons by ionized donors via emission of LO phonons is an efficient relaxation mechanism.