A quantum mechanical theory of superconducting tunnel junctions including noise is developed. The theory is applied to the calculation of the frequency pulling, linewidth of the radiation, and voltage power spectrum in the ac Josephson effect.

We develop a quantitative nonlinear theory of sound amplification by carrier drift in piezoelectric semiconductors and predict an effect of sound automodulation, i.e., quasi-periodical variation of the intensity of monochromatic sound due to the nonlinear interaction of the sound with its own acoustoelectric field.

Free-carrier absorption was observed in intrinsic crystals of strontium titanate when excited by two-photon absorption of laser pulses. The temperature dependence of the recombination time was found to be exponential, with an activation energy of 0.105 eV. This energy may correspond to the depth of the valleys at the edges of the Brillouin zone in the lowest conduction band or to the activation energy of localized traps.

We point out that an exciton and an optical phonon may form a bound state which moves through the crystal. Calculated binding energies and oscillator strengths for this new quasiparticle lend support to recent suggestions that strong exciton-phonon mixing is present in the optical spectra of some ionic crystals.

By simultaneously sending through a quartz sample two coherent light beams having a beat frequency equal to the frequency of the 207-${\mathrm{cm}}^{-1\mathrm{}}$ optical mode of the quartz, we have been able to generate coherent optical phonons with an estimated power of 100 W.

Photomagnetic change in the initial permeability has been investigated in Ga-doped Cd${\mathrm{Cr}}_2$${\mathrm{Se}}_4$. A simple model is shown to account satisfactorily for the experimental data.

An atomic-beam magnetic-resonance apparatus has been used in a test of parity and time-reversal invariance in atomic systems. An upper limit to the permanent electric dipole moment of the cesium atom, $\left|d_{\mathrm{Cs}}\right|<\mathrm{}3.7\mathrm{}\times {10}^{-22\mathrm{}}e$ cm, has been set. This result leads to an upper limit to the electric dipole moment of the electron, $\left|d_e\right|<\mathrm{}3\mathrm{}\times {10}^{-24\mathrm{}}e$ cm.

We report the observation of time distortion of intense laser pulses due to the self-focusing effect. The on-axis shape of pulses propagating in nitrobenzene was measured and compared with a computer solution of the nonlinear wave equation.

We have looked for a possible $\mathrm{CP}$-nonconserving asymmetry in the momentum spectra of the charged $\pi$ mesons in the decay ${K_L}^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$. No significant asymmetry was observed. Making the linear spectrum approximation, we obtain for the $\mathrm{CP}$-nonconserving parameter, ${\sigma }_{\pm }$, +0.001 ± 0.004.

We discuss an expansion of the spinless scattering amplitude $A(s, t, u)$ in terms of the representation coefficients of the Lorentz group. The expansion preserves the cut structure of $A(s, t, u)$ on a term-by-term basis, and is valid for arbitrary values of $s$, $t$, $u$. The expansion parameters are given in terms of Regge trajectory and residue functions.

Sum rules for baryon-resonance octet coupling constants are derived from a model of SU(3)-symmetry breaking suggested by Pakvasa. The available data on ${\mathrm{½}}^{-}$, ${\frac{3}{2}}^{-}$, ${\frac{5}{2}}^{-}$, ${\frac{7}{2}}^{-}$, and ${\frac{5}{2}}^{+}$ octet states is shown to be compatible with the sum rules.

The well-known fact that the existing quantum mechanical formalism is inconsistent with the energy-time uncertainty-relation postulate is shown to play a crucial role in the logical deduction leading to the conclusion that $\mathrm{CP}$ invariance is violated in some neutral kaon decays. It is therefore argued that if one believes in the existence of the energy-time uncertainty relation, then one has to accept that none of the existing experimental facts can unambiguously be interpreted as evidence against the universal validity of $\mathrm{CP}$ invariance.

It is proposed that one measure the diffraction production of the $\rho$ meson by high-energy neutrinos, i.e., the process $\nu \to {\mu }^{-}+{{\rho }_{\mathrm{virtual}}}^{+}$ followed by ${\rho }^{+}$ diffraction scattering. By comparison with $\gamma +p\to {\rho }^0+p$, the $\beta$-decay coupling constant can then be obtained. The process is distinguishable experimentally because of the characteristic low momentum transfer to the nucleon. Numerical calculations indicate that this process should be observable in large heavy-liquid bubble chambers.

Energies of the ${}_{}{}^3{}_{}{}^{}P$ and ${}_{}{}^1{}_{}{}^{}D$ states of ${\mathrm{N}}^{-}$ have been calculated using a first-order wave function designed to include the strongly structure-dependent part of the correlation energy. Comparing the ${\mathrm{N}}^{-}$ calculations to those of other appropriate systems, the remaining correlation energy is reliably estimated and the ${}_{}{}^1{}_{}{}^{}D$ ${\mathrm{N}}^{-}$ state is predicted to be metastable, lying 0.844 eV below the ${}_{}{}^2{}_{}{}^{}D$ state of N. Instability of the ${}_{}{}^3{}_{}{}^{}P$ ${\mathrm{N}}^{-}$ state is predicted.

We have observed Raman scattering from the hybrid plasma mode in $n$-GaAs and its coupling with the Bernstein modes at harmonics of the cyclotron frequency.

Using the ac Josephson effect we have demonstrated experimentally that $\frac{2e}{h}$ is identical in lead, tin, and indium to within 1 part in ${10}^8$.

By studying reflectance spectra in GaAs modulated by a second, intense light beam, we have observed oscillatory structures in the spectra near the energy gap as well as near 3 eV. We conclude that these structures result from a neutralization of the builtin surface field by free carriers created by the intense light beam. The experimental line shape near the band gap is qualitatively very similar to the theoretical prediction for the Franz-Keldysh effect but is shifted to lower energies presumably due to exciton effects.

An optical density of states in amorphous Ge derived from photoemission measurements shows that the maximum in the valence-band density of states is shifted 1.5 eV to higher energy with respect to the crystalline density of states. No structure is observed in the conduction-band density of states for the amorphous material, whereas strong structure is present in the crysalline density of states. Changes observed in the optical properties of Ge on disordering can be explained using these results.

The electronic density of states of amorphous germanium is simulated by that of a dilated germanium crystal having the same density as amorphous germanium (3.9 g/${\mathrm{cm}}^3$). This simulated density of states accounts quite nicely for some recent experimental results obtained by optical and photoemission techniques. The band structure and density of states of a suitable dilated germanium crystal may well be a better starting point for a more sophisticated analysis of the electronic structure of amorphous germanium than their counterparts in normal crystalline germanium.

The intense scattering of light by quartz in the vicinity of the $\alpha -\beta$ transition, first observed by Iakovlev and co-workers in 1955, has been studied by Raman and Brillouin spectroscopy and by visual observation. Our results indicate that the observed "opalescence" does not originate from critical fluctuations of the order parameter but is generated by essentially static domain walls separating microdomains of opposite electrical twins.