By using exact inclusive sum rules we infer that the growth with energy of the total $\mathrm{pp}$ cross section is connected with the mechanism which is responsible for the appearance of a sharp peak near the kinematical boundary in the process $p+p\to p+\mathrm{anything}$. We discuss this mechanism in the context of Regge models and suggest tests of this idea which involve $K^{+}p$ scattering experiments.

The harmonic or sum-frequency power generated in the last coherence length of a low-density atomic species is calculated subject to the condition that the applied electric field be bounded by the multiphoton absorption or ionization limit. It is shown that higher-order polarizations may equal or exceed lower-order polarizations. Calculations are given for generation at 1773 and 1064 Å in Xe, and at 236, 169, and 177 Å in ${\mathrm{Li}}^{+}$.

This thickness dependence of the accommodation coefficient $\gamma$ of unsaturated He I films has been determined by measuring the time constant of a magnetically levitated, slowing, rotating superconducting sphere situated in helium vapor and covered with an unsaturated helium film. The deviation of $\gamma$ from unity and the linear temperature dependence of the experimental values are in direct contrast to the saturated condition. The abrupt drop of $\gamma$ at the film thickness of two atomic layers for all the temperatures that we have measured has been interpreted as a direct evidence of solid layers (or the solidlike layers) of helium film.

Intense relativistic electron beams were propagated around a 180° toroidal sector to study beam dynamics in toroidal fields. The major drift was along $-\overrightarrow{\mathrm{R}}\times \overrightarrow{\mathrm{B}}$ and no $\overrightarrow{\mathrm{E}}\times \overrightarrow{\mathrm{B}}$ drift was observed, in contrast to the case of plasma in toroidal fields. Based on these observations, a method of injection of electron beams into toroidal fields is proposed.

The splay and bend elastic constants of nematic $p$-cyanobenzylidene-$p^{\prime }$-octyloxyaniline have been measured as a function of temperature. The bend constant diverges near the nematic-smectic-$A$ phase change, with the temperature dependence predicted by de Gennes. The splay constant shows no anomaly, as expected.

Equations are derived for the motion of the magnetization and the "spin axes of the Cooper pairs," and solved for the case of unsaturated cw resonance. In general two discrete resonances are predicted, but if a special condition is met, only one occurs. The complete field dependence of the line(s) determines the gap configuration almost uniquely. The predictions are consistent with existing data and in strong conflict with Anderson's theory.

High-field ($H\le 60$ kG) and low-temperature ($T\ge 25$ mdeg K) Mössbauer-effect measurements of the Kondo system $\mathrm{Fe}:Cu$ are reported. The comparison of these results with bulk susceptibility data leads to a polarization, of antiferromagnetic sign, of the electron gas in the Kondo state.

The Mössbauer effect was used to study the effects of neutron irradiation on aluminum doped with ${\mathrm{Co}}^{57}$. Annealing between 32 and 70 K after irradiation at 4.6 K induces in the previously single-line Mössbauer source spectrum a new component with small quadrupole splitting, which has an isomer shift of + 0.40 mm/sec against the original single line. The new component disappears irreversibly on further annealing between 180 and 250 K. This component is interpreted as being due to interstitials trapped in the immediate proximity of the ${\mathrm{Co}}^{57}$ impurity atoms.

An aluminum film formed by evaporation at 25 K onto a similar film previously deposited at room temperature displayed a featureless optical spectrum in the range 0.6-3.5 eV, the characteristic (200) peak being completely absent. A closer analysis showed the absorption to consist of a Drude term ($\hslash {\omega }_p=7.45\mathrm{}$ eV; $\tau =3.4\mathrm{}\times {10}^{-15\mathrm{}}$ sec) and what is believed to be interband absorption, possibly associated with a residual (111) absorption band.

NMR shifts and relaxation times are reported here for ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$ impurity nuclei in a series of liquid ${\mathrm{Al}}_{1-x}{\mathrm{Cu}}_x$:Mn alloys over the composition range $0<~x<~1$ and at temperatures from 1050 to 1425 K. Analysis of shifts and susceptibilities reveals abrupt changes in $d$-spin hyperfine field and orbital susceptibility at the Cu-rich end. A sharply increased value of the relaxation rate for $x\to 1$ is analyzed to give $J_{\mathrm{sd}}=0.82\mathrm{} \mathrm{and} 1.22$ eV for the liquid and solid phases, respectively.

We have observed the Raman scattering from surface polaritons in a thin film (≈ 2500 Å thick) of GaAs on a sapphire substrate. The mode frequency varies as a function of the scattering angle from the TO phonon frequency of GaAs, ${\omega }_{\mathrm{TO}}=270\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, corresponding to forward scattering, to the asymptotic value of 283 ${\mathrm{cm}}^{-1\mathrm{}}$, corresponding to a large scattering angle. The dispersion of the mode frequency was found to be appropriate for the surface polariton of a GaAs film bounded by a sapphire substrate on one side and by air on the other side.

We present the theory of surface polaritons which propagate in a film of a surface-active material placed on a substrate. The theory provides a description of the new mode observed recently by Evans, Ushioda, and McMullen in the Raman spectrum of a GaAs film placed on a sapphire substrate.

At low temperatures and medium excitation levels, a series of emission lines was discovered in silicon slightly doped with phosphorus or boron. Beginning with the bound exciton, the series converges towards the energetic position of the maximum of emission of the condensed electron-hole state. The sharpness of these lines and the characteristic dependence of their intensities on doping level and on excitation level suggest a model of multiple-exciton complexes bound to the impurities.

The pressure dependence of the coupled-mode spectra in potassium dihydrogen phosphase (KDP) was measured at room temperature for hydrostatic pressures from 0 to 9.3 kbar. The soft mode, which is overdamped for all temperatures at atmospheric pressure, becomes underdamped for pressures ≥ 6 kbar. This is the first observation of an underdamped soft mode for a crystal of the KDP class and resolves the question of whether the excitation should be considered as diffusive or oscillatory in nature.

Results are presented for the $c$-axis resistivity of dysprosium in the vicinity of the Néel temperature $T_{\mathrm{N}}$, which provide the first quantitative verification of the theory of scattering of electrons by spin fluctuations above $T_{\mathrm{N}}$ in an antiferromagnet. Immediately below the transition the resistivity can be described by including the effects of phononsmeared superzone-induced band gaps.

Detailed measurements of luminescence lines from optically pumped germanium lead to the determination of the temperature variation of the carrier density and binding energy of an electron-hole liquid. A metallic model of this liquid provides a quantitative description of the data and allows a determination of the compressibility of the liquid.

Total cross sections for ${\pi }^{+}$ and ${\pi }^{-}$ mesons on ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ have been measured for energies between 90 and 860 MeV. Using dispersion relations, values for the effective pion-nucleus coupling constant have been obtained.

Angular distributions of the three tensor analyzing powers have been measured for ($d, p$) reactions on ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. Distorted-wave calculations are inconsistent with the measurements if the deuteron $D$ state is ignored. However, excellent agreement is obtained when the effects of the $D$ state are included. We discuss the dependence of the tensor analyzing powers on incident deuteron energy, $Q$ value, and angular momentum transfer.

The mass excess of ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ has been measured to be 23.657±0.030 MeV using the reaction ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$)${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ at $E\left({}_{}{}^7{}_{}{}^{}\mathrm{Li}\right)=52\mathrm{}$ MeV; this shows that ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ is bound by nearly 1 MeV against neutron emission. Five excited states were also observed at 0.74±0.04, 1.38±0.03, 1.82±0.06, 2.08±0.05, and 2.97±0.04 MeV. The low-lying level structure of ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ was found to be similar to the known negative-parity spectrum of ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$.

It is shown that the short-range part of the generator-coordinate amplitude $f$, which is left after the long-range part proportional to the scattering wave $g$ has been removed, may be expanded to any degree of accuracy, as far as its integral properties are concerned, into a finite sum of well-behaved, square integrable functions. In that sense the amplitude $f$ obeys the same boundary conditions as the scattering wave function $g$. A simple method for solving the Hill-Wheeler equation is presented.