The lowest $T=2\mathrm{}$ state in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ has been found in the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(\alpha ,\gamma ){}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ at an excitation energy of 9338 ± 2 keV in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$. The radiative yield has been measured and the $\gamma$ decay has been studied.

A generalization of the scalar product of the Dirac theory is proposed which together with a recently described generalization of the Dirac equation leads to a simple description of a massive ($m>\mathrm{}0\mathrm{}$), spin-$s$ relativistic field. This theory avoids the difficulties of parity doubling, indefinite metric, and negative energies in the second-quantized formalism, while preserving the consistency and causality of the wave equation in an external electromagnetic field.

In a scintillation-counter experiment on the reaction ${\pi }^{-}+p\to M^0+n$ at 2.4 $\frac{\mathrm{GeV}}{c}$, we have obtained evidence for a neutral meson denoted $M^0\mathrm{}\left(1033\right)\mathrm{}$ with a mass of 1032.6 ± 2.3 MeV and a width of ${16.2}_{-7.5\mathrm{}}^{+4.8\mathrm{}}$ MeV.

The consequences of Feynman scaling are examined for photon spectra at $x=0\mathrm{}$ arising from ${\pi }^0$ decays. A consistency condition on the photon distribution is obtained. The lowtransverse-momentum region is examined in detail and the contribution of bremsstrahlung computed to be $\frac{\left(\frac{k}{{\sigma }_{\mathrm{tot}}}\right)d\sigma }{d^{3}k}=\left(\frac{\alpha }{{\pi }^{2}k_{\perp }^{}{}_{}{}^2}\right)〈{\left(\Delta Q_R\right)}^2〉$, where $\Delta Q_R$ is the final right-moving charge minus the initial right-moving charge. This relation, together with the consistency condition, provides a new means of obtaining pertinent multiplicity information at very high energies.

The recently observed multiple inner-shell Coulomb ionization induced by swift, heavy ions is treated by a semiclassical method. Impact-parameter dependences and multiple ionization probabilities as functions of the projectile energy are given and discussed in relation to experimental data.

We present a method for the conversion of x-ray diffraction data into an electron density which reflects the antisymmetry of the $N$-electron wave function.

Ultrasonic measurements have been made in an oriented smectic liquid crystal. The material was aligned by cooling through the liquid crystal-isotropic liquid transformation in the presence of a 12.4-kOe magnetic field. The ultrasonic attenuation is significantly more anisotropic than it is in nematics. The velocity also has a measurable anisotropy (∼ 5%). The velocities give certain of the elastic constants in de Gennes's theory of the smectic state.

The x-ray diffraction pattern of a shock-compressed material which is in the process of undergoing a crystal structure transformation has been observed for the first time. Pyrolytic BN, explosively shocked to 245 kbar, exhibits a diffraction pattern which indicates that the crystal structure during compression is like that of wurtzite.

A time-differential perturbed angular distribution experiment on the 247-keV level of ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$, excited by the ($d,p$) reaction in ${}_{}{}^{110}{}_{}{}^{}\mathrm{Cd}$ metal, shows a static quadrupole interaction at high temperatures and pronounced effects of radiation damage at lower temperatures.

It is shown that phonon drag determines the limiting low-temperature form of the electrical resistivity of the alkali metals, causing the resistivity to exhibit an exponential, rather than a power-law, dependence on temperature. Including the phonon-drag contribution leads to excellent theoretical agreement with the recent low-temperature resistivity measurements for potassium by Gugan.

Photoconductivity on ($1\overline{1}00$) prism surfaces of ZnO crystals has been measured at low temperatures in ultrahigh vacuum. The spectral distribution between 0.2 and 0.7 eV exhibits two sequences of minima. The periods coincide with the energies of bulk LO phonons and of surface phonons, respectively. Additional evidence for the interaction with surface phonons is given by condensing xenon on the crystal surface. Thereby the period corresponding to the energy of surface phonons is decreased as expected.

Accurate birefringence measurements on monodomain SrTi${\mathrm{O}}_3$ platelets give important information about the fluctuations associated with the second-order structural phase transition. Above the transition, the monodomain character is announced by a birefringence tail caused by anisotropic fluctuations. Because of these, a distinct cusp is observed at the transition temperature $T_a$. Below $T_a$, the difference $〈\varphi _c^{}{}_{}{}^2〉-〈\varphi _a^{}{}_{}{}^2〉$ between mean-square rotations ${\varphi }_c$ associated with the order parameter and orthogonal rotations ${\varphi }_a$ is obtained.

The lowest conduction bands of a number of perovskites are determined principally by the ($\mathrm{pd}\pi$) interaction which mixes the $t_{2g} d$ orbitals of the transition-metal ion with the $p$ orbitals of the oxygen. Because of the planar character of the ($\mathrm{pd}\pi$) interaction, each of the three equivalent $t_{2g}$ conduction bands depends strongly on only two of the components of the wave vector. As a result, the bands possess a two-dimensional character which accounts for the characteristic structure in the density of states and the optical properties of SrTi${\mathrm{O}}_3$, BaTi${\mathrm{O}}_3$, and KTa${\mathrm{O}}_3$.

The linewidth and $g$ value for the conduction-electron spin-resonance-transmission line shape of aluminum was observed to be frequency and temperature dependent. The data are interpreted as a consequence of motional narrowing and many-body exchange in metals with $g$ anisotropy, a many-body parameter for the spin part of the Landau correlation function, and the behavior of a relevant relaxation time.

The variation of $g$ over the Fermi surface leads to a breakdown of Larmor's theorem when scattering is too slow to motionally narrow conduction-electron spin resonance. We show that electron correlations lead to a collective mode whose position is not that of motionally narrowed conduction-electron spin resonance, and whose width would be zero in the absence of scattering. The shift and width of the collective mode are discussed in general and calculated in one experimentally interesting regime.

The scattering of surfons by point mass defects in a solid surface is calculated in terms of field-theoretical scattering theory. Scattering cross sections for incident Rayleigh-mode surfons into other Rayleigh-mode surfons and into one with a total-reflection mode are estimated as functions of incident frequency. It is shown that both of these cross sections have typical resonance structure in the frequency region $\omega \simeq \mathrm{}(1-3)\mathrm{}\times {10}^{13}$ ${\sec }^{-1\mathrm{}}$.

We report the observation of an acoustic phonon mode, usually not Raman active, which is interpreted here as a disorder-activated longitudinal acoustic mode. Because of good matching of lattice constants and nearest-neighbor force constants in the alloy system ${\mathrm{Ga}}_x{\mathrm{Al}}_{1-x}\mathrm{As}$, a simple theory has been successfully applied to obtain information on the electronic states.

Because the optical spectra of substitutional semiconductor alloys are so similar to those of the pure compounds, it is widely believed that the virtual-crystal approximation is accurate, i.e., that fluctuations in the crystal potential are negligible. Investigating the effect of alloying on the spin-orbit splitting, we show that this is not true.

Deep-hole excitations formed in knockout reactions decay rapidly by the ejection of additional nucleons. Other coherent processes that lead to the same final states are discussed. These may be important in some circumstances.

Strikingly improved distorted-wave fits to experimental cross sections are obtained for the ($p,2p$) reaction cross section by including an energy dependence to the two-proton $t$ matrix. The two-proton $t$ matrix used is a local effective $t$ matrix times a factor which reproduces the three-body model energy dependence of a two-proton $t$ matrix resulting from a separable potential.