A new unitary sum rule for $K_S-K_L$ decay is derived by use of a phenomenological $S$ matrix.

A Veneziano model for the odd-normality ($\pi$) contributions to $\pi \rho$ double-charge-exchange scattering is found. In the model, the leading trajectory is not parity doubled and its residues satisfy the factorization condition. An argument is given for the existence of high-mass exotic resonances.

We have developed an improved exchange approximation for use in self-consistent atomic structure calculations and related problems. By adding an inhomogeneity correction to the Kohn-Sham-Gaspar exchange potential, we are able to obtain total energies for atoms that are consistently closer to the Hartree-Fock values than are those given by other recently proposed exchange potentials.

A room-temperature bulk GaAs mixer is used to mix frequencies of pairs of cw vibrational-rotational C${\mathrm{O}}_2$ laser lines, each stabilized to line center. The beat frequencies, in the millimeter-wave region of 50-80 GHz, are measured for 37 pairs of transitions to better than 1 MHz. The deduced rotational constants for the relevant vibrational levels (00°1, 10°0, 02°0) are 25 to 200 times more accurate than the best previous results (from conventional spectroscopy).

We have observed a resonance phenomenon in the fluorescent light from ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ at a frequency corresponding to the interval between the nondegenerate Zeeman components $\beta$ and $f$ of the $4{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ and $4{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ states excited by an electron beam modulated at the corresponding frequency (uhf microwave). The observations can be interpreted as "quantum beats." An observation which we recently described in this way is better considered as a time-dependent level-crossing effect.

Spin conservation in ionizing reactions involving optically oriented $2{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ metastable helium atoms in a helium discharge has been exploited to produce a continous beam of polarized electrons. A beam polarization of (10 ± 0.5)% is measured, with beam current 0.2 μA. Electrons extracted from the pulsed discharge afterglow have polarization (14 ± 0.7)%. The apparatus is simple and versatile, and should be readily adaptable to atomic and nuclear scattering experiments.

The equations describing the propagation of optical radiation through a medium of two-level atoms are presented in a way that emphasizes their relation to Poynting's theorem. Two classes of solutions which propagate without distortion are discussed. These solutions, together with the well-known hyperbolic secant solution, are analogous to the three possible types of motions of a simple pendulum.

We have utilized the trapping of electrons on quantized vortex lines in rotating He II to permit detection of single lines in order to study the appearance and disappearance of the first few lines in a capillary rotating about its axis. It seems likely that an extension of the method will permit study of the spatial distribution of vortices in rotating vessels of He II.

Experimental observation of the resonant mode-mode coupling type of nonlinear decay instability and parametric amplification of cyclotron-harmonic waves is reported. The instability is due to the scattering of finite amplitude waves.

We describe a variation of Veksler's "collective-ion acceleration" principle by which electrons of energy 100-1000 MeV are injected in a static magnetic field to form an electron ring of rather large initial diameter; the electron ring then is subjected to successive axial accelerations taking place at constant radius in a decreasing magnetic field, and decelerations taking place in an increasing magnetic field under adiabatic conditions. The functional dependence of the electrons' azimuthal mechanical momentum on the axial magnetic field is different for the two field configurations, and the result is a net compression of the electron ring at the end of each stage of axial acceleration and deceleration.

An algorithm is presented for obtaining electron-gas stability information from neutral-plasma literature.

We report a significant anisotropy of the $g$ factor of the free hole in uniaxially stressed Ge which represents the first observation in any band structure of the $q$ term postulated by Luttinger in the valence-band Hamiltonian. It is shown that this effect arises from the spin-orbit splitting $\Delta \left(\Gamma _{15}^{}{}_{}{}^{-}\right)$ of the nearby $\Gamma _{15}^{}{}_{}{}^{-}$ conduction band. The measurements yield the value $\Delta \left(\Gamma _{15}^{}{}_{}{}^{-}\right)=0.15\mathrm{}\pm 0.03$ eV.

Using the nonlocal and energy-dependent Heine-Abarenkov model potential we calculated the phonon spectrum of Li. A good agreement with the experimental values is obtained. We have also considered the importance of the $l$ dependence of the model potential.

The exchange-enhanced magnetic susceptibility of Sc and ${\mathrm{Ni}}_3$Ga decreases strongly when small amounts of nonmagnetic impurities are added. The decrease is a linear function of the spectroscopic spin-orbit energy of the impurity at constant valency and has the same origin as the decrease of the Curie temperature of Ni in dilute Ni:Pd and Ni:Pt.

We report the first determination of the Ni hyperfine field in the ferromagnetic state of ordered ${\mathrm{Ni}}_3$Fe to be -167 kOe at 1.4°K. This value is significantly larger in magnitude than that in disordered dilute solid solutions of Fe in Ni. We use, for the first time, an NMR spin-echo spectrum to deduce a value of the long-range-order parameter and suggest the usefulness of NMR data to characterize the atomic disordering in alloy systems.

The response function $\chi (\overrightarrow{\mathrm{K}},\omega )$ of nickel has been calculated over a wide range of temperatures on the basis of a tight-binding band structure with allowance for electron-electron interactions. Spin-wave broadening and renormalization, the steady development of $\chi$ through $T_c$ [away from the singularity at $\chi \mathrm{}(0,0)]$, and the occurrence of "vestigial" spin waves above $T_c$ are all well illustrated. With a Hubbard-Gutzwiller-Kanamori $I_{\mathrm{eff}}\sim 0.6$ eV ${\mathrm{atom}}^{-1\mathrm{}}$ there is quite good absolute agreement with experiment, this agreement being improved if a suitably $K$-dependent $I_{\mathrm{eff}}\mathrm{}\left(K\right)\mathrm{}$ be introduced.

The far-infrared absorption spectrum of crystalline alpha oxygen ($\alpha -{\mathrm{O}}_2$) has been measured in annealed samples up to 20 mm thick. The prominent feature of the spectrum is a temperature-dependent absorption near 27 ${\mathrm{cm}}^{-1\mathrm{}}$ which appears to be an anti-ferromagnetic resonance mode, the first such collective excitation to be observed in a molecular solid.

Large angles between the local direction of magnetization and that of the applied magnetic field, which have been found in experiments involving the embedding of excited nuclei in Fe or Ni foils, are explained in terms of the crystalline imperfections caused by the foreign nucleus when it penetrates the ferromagnetic lattice. A rather crude estimation yields the same results for line or point defects, and it is concluded that the sine of these angles should decrease, with increasing magnetic field $H$, roughly as $\frac{1}{H}$.

By comparing new experimental results with calculations, it is shown that the levels above the ½ ${}_{}{}^{-}{}_{}{}^{}[5,$ 3, 0] ground-state band in ${}_{}{}^{233}{}_{}{}^{}\mathrm{Pa}$ and ${}_{}{}^{231}{}_{}{}^{}\mathrm{Pa}$ may be interpreted as resulting from the ${\mathrm{½}}^{+}$[6, 6, 0], the ${\frac{3}{2}}^{+}\mathrm{}[6,5,1]\mathrm{}$, and the ${\frac{5}{2}}^{+}\mathrm{}[6,4,2]\mathrm{}$ bands involved in a three-band Coriolis interaction.

An x-ray polarimeter sensitive to x rays in the energy range from 6 to 18 keV, flown above the atmosphere on 27 July 1968, was used both to set an upper limit on the polarization of Sco X-1 and to check for spurious indications of polarization which might result from the anisotropy of the cosmic rays. Within the statistical limitations of the data, no evidence was found for spurious background polarization.