The reflection coefficient of phonons at a boundary between several dielectric crystals and liquid helium has been measured by the heat-pulse technique. The reflection coefficient is found to be smaller for transverse phonons than for longitudinal.

Observed phonon structure in the tunneling density of states of superconducting La films ($T_c={4.9}^{\circ }\mathrm{K}$, $\frac{2\Delta }{k{T}_c}=3.8\mathrm{}$) contains resolvable detail not reported previously, with maximum deviations from the BCS prediction amounting to 1.7%. The McMillan-Rowell method of analysis produces a phonon spectrum ${\alpha }^{2}F\left(\omega \right)$ characterized by parameters which predict $T_c=5.0\mathrm{}$ °K via the McMillan equation. Implications of this agreement are discussed.

The $F$ and $F^{+}$ bands in BaO at 77°K are observed to be at 2.3 and 2.0 eV, respectively. The ground state for the $F$ centers is about 0.1 eV below the conduction band. Above 77°K the $F$ centers are partially ionized so that the observed band is composite. The released electrons give rise to a free-carrier absorption in the near infrared. The configuration-coordinate diagram shows a barrier to recombination, and recombination by tunneling is observed. These $F$ centers are believed to be the long sought-after donors in oxide-coated cathodes.

It is shown that two-step, two-wave mixing makes a substantial contribution to the total three-wave mixing process in a noncentrosymmetric crystal. The efficiency of generating $2{\omega }_1-{\omega }_2$ was observed as a function of the difference frequency ${\omega }_1-{\omega }_2$, the electric polarization vector, and the propagation direction. This method allowed the determination of the true third-order susceptibility ${\chi }^{\left(3\right)}$, in both sign and magnitude, in terms of ${\left[{\chi }^{\left(2\right)}\right]}^2$.

A completely real-space solution of the tight-binding Hamiltonian has allowed a realistic interpretation of ion-neutralization spectroscopy and some ultraviolet photoelectron spectroscopy data in terms of the surface density of states at transition-metal surfaces. The rms width of the $d$-band density of states decreases as the square root of the coordination number of surface atoms. The extent to which this is observed depends on the surface sensitivity of the experimental technique.

We have studied neutron Pendellösung fringe patterns within the Bragg reflection from perfect silicon crystals. The patterns as obtained with a full-spectrum incident beam show that the coherent wave front of the neutron radiation must be considered as spherical rather than planar, and also that the crystals under study possess a uniformly curved distortion. The extended fringe patterns permit a precision determination of the coherent nuclear scattering amplitude for silicon of 0.41491(10)×${10}^{-12\mathrm{}}$ cm per nucleus.

An improved phenomenological fit to the experimental data on the reaction $d+d\to d+n+p$ has been achieved based on one-nucleon-exchange quasifree nucleon-deuteron scattering by including a large off—energy-shell correction in the nucleon-deuteron scattering amplitudes.

The mean lifetime of the $0_2^{}{}_{}{}^{+}$ state of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ is found to be 0.97 ± 0.10 nsec. This corresponds to a monopole strength $\rho =(2.6\mathrm{}\pm 0.3)\times {10}^{-2\mathrm{}}$ and $B(E2:{O_2}^{+}\to {2_1}^{+})<\mathrm{}2.0\mathrm{}{e}^2 {\mathrm{F}}^4$. The $E0$ strength can be accounted for with standard shell-model wave functions using a state-dependent monopole effective charge derived from isotope-shift data.

We discuss and apply a general method for measuring the difference of polarization observables from their maximum allowed value. Relatively crude double-scattering experiments determine the proton polarization for 12-MeV $p-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ scattering with an absolute uncertainty of 1 part in 1000. It is anticipated that these concepts can be applied to higher-energy reactions where experiments do not lend themselves easily to precision measurements and where basic symmetries appear more likely to break down.

We have studied the ($p,t$) reaction on ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ at $E_p=41.7\mathrm{}$ MeV. The observed yields to the $0^{+}$, $T=0\mathrm{}$ states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ are at variance with distorted-wave Born-approximation predictions using the coexistence model to describe the initial and final states of the targets. By use of wave functions which employ a more extensive set of configurations, satisfactory agreement with the observed yields is achieved for the reaction ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}\mathrm{}(p,t)\mathrm{}{}_{}{}^{16}{}_{}{}^{}\mathrm{O}$.

Data on charged-particle multiplicities in 200-$\frac{\mathrm{GeV}}{c}$ $\mathrm{pp}$ interactions are compared with data at lower energies and with predictions of current models. Fragmentation models are shown to be in substantial agreement with present results, but a multiperipheral view cannot be excluded. Further tests are suggested.

We report on a measurement of the missing-mass, ${\mathrm{}\left(\mathrm{mm}\right)\mathrm{}}^{-}$, spectrum from the reaction ${\pi }^{-}+p\to {\mathrm{}\left(\mathrm{mm}\right)\mathrm{}}^{-}+p$ at 8 GeV. The data contain 6500 events in the $R$ peak ($M^2=2.72\mathrm{}\pm 0.02$ Ge${\mathrm{V}}^2$, $\Gamma =139\mathrm{}\pm 31$ MeV). The $R$ shape is consistent with either a single Breit-Wigner or several wide resonances, as suggested by bubble-chamber experiments, but inconsistent with the series of narrow resonances reported by the CERN missing-mass group.

$K$-shell ionization cross sections have been measured at 2.04-MeV incident electron energy for 32 elements from V ($Z=23\mathrm{}$) to Bi ($Z=83\mathrm{}$). Measured cross sections drop from a value of 353 b at V to 9.9 b at Bi. The general trend of the $Z$ dependence of the cross sections is in agreement with theoretical predictions of Kolbenstvedt. However, variations in cross sections by as much as 30% from one element to the next are not accounted for by the theory.

The attenuation of longitudinal ultrasound along the [100] direction in Nb, resistivity ratio $\frac{R_{300}}{R_0}=5200\mathrm{}$, has been measured with precision at low temperatures. The total attenuation in the normal state can be accurately deduced by a BCS calculation, with a single gap $2\Delta \mathrm{}\left(0\right)=(3.52\mathrm{}\pm 0.02)k{T}_c$, from the measured superconducting attenuation. No experimental evidence has been found for the existence of either a smaller or a larger gap.

We observe that charging the interface of a silver film on mica at a frequency $\omega$ modulates the conductance of the film at both $\omega$ and $2\omega$. Relative magnitudes and phases of the observed modulations, and their dependence on a superimposed dc charge, are consistent with a field-effect model assuming scattering of conduction electrons by surface charges, if the latter occur in patches that scatter the electrons coherently.

The melting temperatures of IV-IV, III-V, and some II-VI crystals are predicted with an accuracy generally better than 10%. Only empirical data for Si are used to fix scaling constants.

It is shown that a relationship exists between the coefficient describing the infrared lattice absorption and the ionic contribution to the second-order electric susceptibility in a polar noncentrosymmetric crystal. By analyzing the available data of the latter it is concluded that two-phonon sidebands in the infrared absorption are due to the second-order dipole moment in all the III-V compounds and to the third-order potential in ZnO and CdS. Further, the magnitude of the integrated infrared absorption coefficient in a cubic homopolar IV-IV semiconductor is discussed.

We report NMR and double resonance studies of $\mathrm{Cu}\mathrm{Co}$ in which we resolve satellites due to three shells of Cu near neighbors around isolated Co impurities. The satellite positions show that the spatial form of the spin polarization oscillates with distance and that the conduction electrons on these atoms contribute about - 8% of the total impurity susceptibility. The splittings are measured versus temperature from 1.5 to 450 K.

Systematic trends in the transport properties of a series of slightly Eu-rich EuS crystals, which strongly suggest that conduction occurs in a band tail, are reported and analyzed. A quantitative model for transport in band tails is developed. The model achieves good agreement with the high-temperature resistivity and Hall coefficient of our samples, and gives accurate predictions of their low-temperature properties.

Photoelectron energy distributions from clean, polycrystalline tungsten reveal a surface-sensitive peak about 0.4 eV below the Fermi energy. This peak, which is identified as a surface state, rapidly decays during gas adsorption, and concomitant growth of a new peak at ∼2.5 eV below the Fermi energy is observed. Over the energy range of the surface-state peak, the strength of surface-state emission relative to bulk emission decreases with increasing photon energy. These results quantitatively substantiate existing field-emission data and qualitatively agree with model photoemission calculations.