We have studied the energy distribution of electrons photoemitted from surface states on the cleaved (111) face of a 0.001-Ω-cm $n$-type Si crystal. We find a 1.8-eV-wide surface band with a peak at 1.1 eV and a shoulder at 0.5 eV below the Fermi energy containing about 8×${10}^{14}$ electrons/${\mathrm{cm}}^2$, i.e., approximately one electron per surface atom. The strong peak lies below the valence-band maximum at the surface. The surface nature of this structure is confirmed by its disappearance when exposed to vacuum contamination at ${10}^{-10\mathrm{}}$ Torr or to oxygen.

X-ray photoelectron spectroscopic measurements show that the valence bands of cuprous halides are composed of two separate bands. The transition matrix elements are taken into account in the analysis of the spectra based on the tight-binding approximation for the valence band. It is found for CuCl that the major part of the upper band arises from the $3d$ state of copper and the major part of the lower band from the $3p$ state of chlorine.

We present room-temperature thermoreflectance spectra of NaCl, KCl, NaBr, KBr, RbBr, KI, and RbI crystals. Extension of these measurements at 90°K for RbI has put in evidence the Rydberg series up to $n=4\mathrm{}$ of the ${\Gamma }_1$ exciton. It has been possible, then, to determine the energy gap ($E_G=6.36\mathrm{}$ eV), the exciton binding energy ($E_0=0.56\mathrm{}$ eV), and the electron effective mass (${m_e}^{*}\cong 0.57m_e$) for RbI.

Single-crystal x-ray investigations reveal charge localization in the insulating phases of ${\mathrm{Ti}}_4$${\mathrm{O}}_7$ and ${\mathrm{V}}_4$${\mathrm{O}}_7$. Chains of $M^{3+}$ and $M^{4+}$ sites run parallel to the pseudorutile $c$ axis, whereas the metal valences are disordered in the metallic phases. The 3+ and some of the 4+ sites form metal-metal pair bonds, and the unpaired 4+ sites have one short metal-oxygen distance.

Peaks found in the attenuation of transverse and longitudinal ultrasonic waves in RbMn${\mathrm{F}}_3$ below the Néel temperature are identified as due to antiferromagnetic resonance on the basis of their temperature-frequency relation and magnetic field dependence. The temperature dependence of antiferromagnetic resonance has thus been determined for $0.1°\mathrm{K}\lesssim T_{\mathrm{N}}-T\lesssim 4°\mathrm{K}$, where $T_{\mathrm{N}}$ is the Néel temperature.

It is pointed out that Garvey and Kelson's mass formulas, which relate masses of adjoining nuclides, hold remarkably well for $\Lambda$ separation energies of light hypernuclei. The binding energies of a number of hypernuclei in the $p$ shell are predicted, including the controversial cases of ${}_{\Lambda }{}^6{}_{}{}^{}\mathrm{Li}$ and ${}_{\Lambda }{}^9{}_{}{}^{}\mathrm{B}$.

Using an example of Press and Bardeen, Newman-Penrose quantities of the electromagnetic field in a Schwarzschild background are related to a differential conservation law and hence changes result from a flux. There is no discontinuity in the quantities resulting from a sudden change in dipole moment; there is no singular surface which moves out at $\frac{1}{3}$ the speed of light. It is suggested that for Newman-Penrose quantities to exist, multipole moments must approach a limit as $\frac{1}{u}$, $u\to -\infty$.

We have measured the cross sections at 90° c.m. for ${\pi }^{\pm }$ and ${\pi }^0$ photoproduction with polarized photons. The photon energies ranged from 0.8 to 2.2 GeV. We compare the resonant "bumps" in the cross section with theoretical models. The measured asymmetry agrees with a quark-model calculation though the predicted cross sections are low.

An improved cross-section upper limit of 1.9 times that of $V-A$ theory is determined for the reaction ${\overline{\nu }}_e+e^{-}\to {\overline{\nu }}_e+e^{-}$. The target, a 7.84-kg plastic scintillator, was enclosed by a composite 330-kg NaI and 2200-liter liquid anticoincidence detector, and was operated in a fission ${\overline{\nu }}_e$ flux of 2.2×${10}^{13}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$. We note some constraints which this limit imposes on theoretical conjectures.

We present the results of a calculation of a part of the direct-emission amplitude in $K^{\pm }\to {\pi }^{\pm }{\pi }^0\gamma$ for which an unambiguous, finite, gauge-invariant expression is obtainable in terms of known parameters. The amplitude produces a small distortion of the Dalitz plot through its destructive interference with the bremsstrahlung amplitude.

This work demonstrates a remarkable regularity for the asymmetry parameter ${〈\frac{{\gamma }_s}{{\gamma }_c}〉}_a$ of all charged secondaries in multiparticle processes, i.e., ${〈\frac{{\gamma }_s}{{\gamma }_c}〉}_a={n_s}^{-0.58\mathrm{}}g\left(E_p\right)$, where $n_s$ and $E_p$ are, respectively, the number of shower particles and the incident energy for a given multiparticle event. We show a simple derivation of $g\left(E_p\right)$ in terms of the emission model and discuss the implications of our results as they relate to the concept of leading particles.

Some implications of neutrinos having nonzero rest masses and having finite lifetimes are considered.

The momentum distributions of the recoil nucleon (spectator) in the reaction $\overline{p}+d\to n+\left(N\overline{N}\right)$ have been calculated taking into account the possible levels in the $N\overline{N}$ system. The comparison of the theory with the experimental data on $p$ annihilation at rest shows the existence of a $\overline{p}n$ bound $D$ state with quantum numbers $J^{\mathrm{PG}}=1^{-+}$.

It is shown that the anomalous constant $S$ associated with the soft ${\pi }^0\to 2\gamma$ decay amplitude is determined by a product of high-energy electroproduction and annihilation cross sections. A similar result holds for the coupling of the trace of the stress-energy tensor to photons. Wilson's theory of broken scale invariance is assumed. We observe that the Fritzsch-Gell-Mann algebra of bilocal operators uniquely specifies disconnected contributions, and, in particular, implies $S=\frac{1}{6}$, the quark field-theoretic value.

It was found that $K$ x rays accompanying $K$ conversion of retarded 177-keV (predominantly $M1\mathrm{}$) transitions from the 316-keV ($T_{\frac{1}{2}}=0.66\mathrm{}$ μsec) nuclear state of highly deformed ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$ have small anisotropic angular distributions with respect to the direction of $\gamma$ radiations emitted subsequent to $K$ conversion. The result is explained as a first-order effect of the static quadrupole moment of the nucleus on the $K$-shell electron wave function.

Si $K$ x rays are observed when solid Si is bombarded by 160-260-keV ${\mathrm{Ar}}^{++}$ ions. The production of such x rays is interpreted in terms of the Fano-Lichten model, and a double-scattering mechanism whereby Si $K$ vacancies are produced by electron promotion to an Ar $L_{2,3}$ vacancy formed in a prior collision.

A new method for determining planar continuum potentials from planar channeling data has been developed. Preliminary experiments have been done for 1.8-MeV $\alpha$ particles in [111] gold planar directions from which the continuum potential has been deduced.

Generation and detection of ultrasonic spin echoes (phonon echoes) and of ultrasonically induced rf magnetic field spin echoes are reported. With the latter, signal-to-noise improvements of 2 orders of magnitude were found over direct ultrasonic absorption spectroscopy. The effects of momentum conservation selection rules are discussed, as are properties and applications of the various echoes.

We have studied the behavior of 21.6-MeV I ions undergoing proper axial channeling (hyperchanneling) in Ag. Ions of this special class traverse the crystal within a single axial channel and as a result exhibit conspicuously lower energy losses and an order of magnitude smaller acceptance angles than ordinary axially channeled ions. Analysis of the results indicates that hyperchanneled ions provide a new means for studying multiple scattering radiation damage, and ion-atom potentials in solids.

The splittings of $p_{\frac{3}{2}}$ atomic core levels due to internal electric field gradients have been calculated for the case of ${\mathrm{Tm}}^{3+}$ ions in thulium ethyl sulphate and shown to be measurable by electron spectroscopy. The splittings could be about 1 eV under favorable conditions.