Superfluid flow in restricted geometries is discussed in the framework of the Landau quasiparticle theory. A recently observed linear temperature dependence of ${\rho }_n$ for helium flowing in powders is explained in terms of a model geometry which can be fairly described as "zero-dimensional." Further experiments are suggested for exploring other features of restricted geometries and testing the zero-dimensional model.

Critical phenomena in films of finite thickness are considered. A detailed scaling theory, with allowance for distinct exponents $\lambda$ and $\theta =\frac{1}{\nu }$ for the critical-point shift and rounding, respectively, is confirmed by exact calculations on $d$-dimensional ferromagnetic spherical models and ideal Bose fluids with various boundary conditions. Isingmodel results and existing data on real helium films are consistent with the theory.

An investigation of x-ray scattering, when the Bragg condition is nearly satisfied, reveals the possibility of studying phonon phenomena at momenta as small as ${10}^4$ ${\mathrm{cm}}^{-1\mathrm{}}$. A closer study of elastic Bragg scattering in that region provides an explanation for the previously observed "coherent crystal radiation."

A number of unusual phenomena occur in ${\mathrm{O}}^{16}$ + ${\mathrm{C}}^{12}$ induced reactions at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=19.7\mathrm{}$ MeV. We suggest an interpretation of these effects in terms of a molecular resonance.

We identify 27 excited states of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ in the energy range 10.4-12.5 MeV from the photoneutron spectrum of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ irradiated with 12.5-MeV bremsstrahlung. These levels are probably associated with the promotion of one of the $1f_{\frac{7}{2}}$ valence neutrons into the continuum. The distribution of radiation strength in this region suggests the presence of a single-particle resonance in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ at ∼ 10 MeV.

We report a study of isobaric-analog states excited in the ($p, d$) and ($d, t$) reactions on ${}_{}{}^{92,94,96}{}_{}{}^{}\mathrm{Mo}$ and in the reaction ${}_{}{}^{98}{}_{}{}^{}\mathrm{Mo}(p, d){}_{}{}^{97}{}_{}{}^{}\mathrm{Mo}$. We observe a large decrease in $l=1\mathrm{}$ hole strength with increasing mass number and fluctuations in the ratios $\frac{C^2{S}_n(p, d)}{C^2{S}_n(d, t)}$. The first effect is discussed in terms of mixing with the dense spectrum of $T_{<}$ levels in the region of the isobaric-analog states.

The trinucleon bound-state energy, wave function, and charge form factor are calculated from a direct solution of the complete set of Faddeev equations. The nucleon-nucleon interaction (effective in the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}-{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$ states) is given by the Reid soft-core potential. We find $E_B=6.7\mathrm{}$ MeV, $P\left(S\right)=89.7\%$, $P\left(S^{\prime }\right)=1.7\%$, and $P\left(D\right)=8.6\%$. $\left|{F_{\mathrm{Ch}}}^{{}_{}{}^3{}_{}{}^{}\mathrm{He}}\right(Q^2\left)\right|$ (calculated) is similar to the approximate result of Tjon, Gibson, and O'Connell, and has a minimum at $Q^2=15.5\mathrm{}$ ${\mathrm{fm}}^{-2\mathrm{}}$.

Four-dimensional potential energy surfaces have been calculated in the asymmetric two-center model for ${}_{}{}^{252}{}_{}{}^{}\mathrm{Fm}$, ${}_{}{}^{258}{}_{}{}^{}\mathrm{Fm}$, ${}_{}{}^{264}{}_{}{}^{}\mathrm{Fm}$, and ${}_{}{}^{236}{}_{}{}^{}\mathrm{U}$. Symmetric fission is found to be preferred in ${}_{}{}^{258}{}_{}{}^{}\mathrm{Fm}$, consistent with a recent observation; symmetric mass division is strongly preferred in ${}_{}{}^{264}{}_{}{}^{}\mathrm{Fm}$. Asymmetric fission is preferred in ${}_{}{}^{252}{}_{}{}^{}\mathrm{Fm}$, and in ${}_{}{}^{236}{}_{}{}^{}\mathrm{U}$ for which the fission path is investigated in more detail. The development of asymmetry in the fission of ${}_{}{}^{236}{}_{}{}^{}\mathrm{U}$ is described.

The suggestion of de Broglie and Vigier that an "intermediate shift" might be expected to be obtained in the Goos-Hanchen effect, for plane polarized beams having components both parallel and perpendicular to the plane of incidence of the totally reflective surface, is shown to be untenable. Their quoted experimental results are adequately explained classically.

The position of the $R\left(0\right)\mathrm{}$, $R\left(1\right)\mathrm{}$, and $R\left(2\right)\mathrm{}$ lines of the 3874-Å band of interstellar CN in the spectrum of the star $\zeta$ Ophiuchi were scanned with a Fabry-Perot interferometer. The Doppler width (full width at half-maximum) of the $R\left(0\right)\mathrm{}$ line is 28 mÅ. At the expected position of the $R\left(2\right)\mathrm{}$ line an absorption feature was found with an equivalent width of 0.077 ± 0.055 mÅ which implies a temperature of ${2.9}_{-2.1\mathrm{}}^{+3.4\mathrm{}}$ K for the cosmic background radiation at 1.32 mm. A conservative interpretation of the data is simply to give an upper limit ($2\sigma$) of 3.8 K to this temperature.

An analytic expression for the $2^l$-pole static electric polarizability ${\alpha }_l$ of an atom is obtained in a Coulomb-like approximation. Core effects are neglected and, for simplicity, we consider only $s$-type valence electrons. Accurate values are obtained for the dipole and quadrupole polarizabilities of the alkali atoms and of four alkalilike excited states. Values close to those obtained from coupled Hartree-Fock calculations are computed for several divalent systems.

A transient two-photon process is observed in the infrared which exhibits all the co-operative properties associated with superradiant two-level systems. It arises when a cw laser beam excites a molecular sample whose level degeneracy is suddenly removed by a Stark field. The resulting emission, which heterodynes with the laser, gives precise ground- and excited-state Stark splittings, and decays with a homogeneous relaxation time since Doppler dephasing effects are absent in forward scattering.

We have determined experimental differential cross sections for elastic scattering and the $n=2\mathrm{}$ excitation in ${\mathrm{H}}^{+}$-on-H collisions at an impact energy of 1 keV and compared the results with previous theoretical calculations.

The absorption coefficients of 1.15- and 3.39-μm radiation for a homogeneous H-He plasma have been measured in the temperature range $14\times {10}^3<~T<~20\times {10}^3°$K and electron density range $8\times {10}^{16}<~n_e<~5\times {10}^{17}$ ${\mathrm{cm}}^{-3\mathrm{}}$, where the major absorption mechanisms are electron-ion inverse bremsstrahlung and neutral-atom photoionization. The measured values compare well with those obtained from theoretical calculations for a gas in thermodynamic equilibrium.

The ultrasonic attenuation and velocity of longitudinal waves in the nematic liquid crystal $N-p$-methoxybenzylidine-$p$-butylaniline have been measured as a function of temperature and applied magnetic field at 3.5 MHz, between 17 and 65°C. The orientational anisotropy of the attenuation is strongly temperature dependent in the nematic phase. The velocity shows a 9% dip in the region of the transition; no anisotropy was observed within the 1% accuracy of the measurements.

A new variational wave function is proposed for the ground state of Bose liquids. It consists of the optimized Jastrow function multiplied to exponentials of three-particle functions. The form of the latter is determined variationally in a formal analysis carried out for the weakly interacting Bose gas. Its appearance implies the summation of a new class of diagrams beginning with fourth-order terms in the interaction strength. Several calculations for realistic systems are proposed.

We study theoretically the higher-order corrections in $\Delta \left(\overrightarrow{\mathrm{r}}\right)$, the superconducting order parameter, to the flux-flow conductivity of dirty, type-II superconductors. It is shown that the Thompson term (i.e., the anomalous term) in the flux-flow conductivity is extremely sensitive to the higher-order corrections and decreases rapidly in the vortex state, while the Caroli-Maki term is affected only slightly by the higher-order corrections.

We investigate the ac conductivity of glasses due to atomic and electronic hopping between sites with random space and energy separations. Several examples are considered including the structural model of glasses recently introduced by Anderson, Halperin, and Varma, and by Philips. We find that glassy materials should quite generally exhibit a nearly linear conductivity-frequency relationship. The details of any particular conductivity mechanism should be contained in the deviation from linearity.

It is shown that the model of interrupted strands offers a simple explanation for the temperature dependence of one-dimensional conductors. An array of small metallic particles is used to simulate the essential properties of the model.

A theory of surface magnetoplasmons in semiconductors is developed with the inclusion of retardation for the geometry in which the magnetic field is parallel to the surface and the direction of propagation is perpendicular to the magnetic field. If the background dielectric constant ${\epsilon }_{\infty }$ lies in a suitable range for a given value of the magnetic field, gaps appear in the dispersion relation for the surface magnetoplasmons. The possible experimental observation of these gaps is discussed.