We propose the measurement of reactions of the type $p_1+p_2\to q_1+q_2+$ anything at high energy in the region in which the produced particles $q_1$ and $q_2$ can be regarded as "fragments" of the incident particles $p_1$ and $p_2$, respectively. Dependence of the cross section on the angle between transverse parts of the vectors ${\overrightarrow{\mathrm{q}}}_1$ and ${\overrightarrow{\mathrm{q}}}_2$ would indicate that the Pomeranchuk singularity contains Regge-cut contributions.

Motivated by scaling considerations we formulate a theory of $K_{l3\mathrm{}}$ decay based on the Kemmer equation. We find that our theory (1) has a symmetry-breaking parameter of order 10-30% which agrees with experiment, (2) makes a definite testable prediction of a kinematic zero at $t={(m_K+m_{\pi })}^2$ in the "effective" scalar form factor, and (3) yields a modified Callan-Treiman relation which improves agreement with experiment.

We show that if a Hamiltonian symmetry is realized by Goldstone bosons then, in general, one does not expect the $S$-matrix and matrix elements of currents to be analytic functions of the symmetry-breaking parameters. This modifies the nonrenormalization theorems for vector form factors and some theorems of Dashen and Weinstein.

Using the soft-pion technique with partial conservation of the axial-vector current and the algebra of currents, we express the amplitudes for $\gamma +\gamma \to n{\pi }^{+}+n{\pi }^{-}$ in terms of the spectral functions of the vector and axial-vector currents and calculate the cross sections for $\gamma +\gamma \to n{\pi }^{+}+n{\pi }^{-}$, $e^{\pm }+e^{-}\to e^{\pm }+e^{-}+n{\pi }^{+}+n{\pi }^{-}$, and $e^{+}+e^{-}\to n{\pi }^{+}+n{\pi }^{-}+\gamma$. Gauge invariance is maintained throughout the calculation if, and only if, Weinberg's first sum rule is valid.

The comparison between experimental values of the electric field gradient in neptunyl and uranyl complexes allows the derivation of a simple expression for the inner Sternheimer factor in Np. Its evaluation using relativistic expressions for the hyperfine interactions gives the result $R_{5f}=0.35\mathrm{}\pm 0.1$. An early theoretical estimate is in poor agreement with this number.

The $3Z+2$-dimensional integral for scattering of charged particles by $Z$-electron atoms, which is obtained in the Glauber approximation, is reduced to a one-dimensional integral. Consequently, the approximation may be applied with relative ease to elastic and inelastic transitions of a wide variety of atoms.

Van Brunt and Zare have noted that polarized spectral lines might be observed from many types of dissociative collisions which produce excited atomic fragments and that studies of this polarization could prove to be valuable in determining the angular distribution of the fragments. We have observed that such polarization does, indeed, exist in the ${\mathrm{H}}_{\alpha }$ line produced by dissociative charge transfer of ${\mathrm{He}}^{+}$ + ${\mathrm{H}}_2$ collisions. Measurements have been made at 90° to the beam direction in the energy range from 45 to 700 eV.

Brillouin and Rayleigh scattering have been studied in a gas mixture of S${\mathrm{F}}_6$ and He at various concentrations. A strong coupling exists between the concentration and pressure fluctuations in the mixture that produces a heavy damping of the thermal sound-wave excitations and prevents them from propagating adiabatically. Consequently, a fully coupled solution of the hydrodynamic equations is necessary to describe the spectrum accurately.

We calculate a general expression for anomalous resistivity due to weak electrostatic turbulence in a plasma. In the case of ion acoustic turbulence, it is shown to reduce to the heuristic result of Sagdeev. Applications to perpendicular collisionless shock experiments are discussed.

This Letter introduces infinite-order accurate and efficiently implementable Galerkin (spectral) approximations to time-dependent incompressible flows within slabs, spheres, and cylinders with either rigid no-slip or free-slip boundaries. The unusual choice of Chebyshev polynomials as Galerkin expansion functions is crucial for the efficiency of the method.

It is shown that the principal process of de-excitation of the ${\mathrm{He}}^{+}\mathrm{}\left(2s\right)\mathrm{}$ ion at a metal surface is its conversion to doubly excited ${\mathrm{He}}^0$ by resonance capture of an electron from the solid, followed by autoionization to produce ${\mathrm{He}}^{+}\mathrm{}\left(1s\right)\mathrm{}$ and a fast electron. The ejected electron is faster when produced near a metal surface than when produced in free space. The energetics of this two-stage process provides a detailed corroboration of previously studied interactions of atomic particles with metal surfaces.

Photoemission energy distributions have been measured for liquid and crystalline Au using photon energies from 16.8 to 40.8 eV. The nature of optical excitations is observed to change from direct interband transitions to local or nondirect transitions upon passing from the crystalline to the liquid state. For liquid Au, we measure $d$ bands of width 6 eV, with an edge about 1.6 eV below the Fermi level $E_{\mathrm{F}}$ and two peaks in the optical density of states at 3.2 and 5.8 eV below $E_{\mathrm{F}}$.

We report the observation of Azbel'-Kaner cyclotron resonance in the limit where distinct transitions between quantized levels have to be considered. A multiplet structure is found in the subharmonic resonances arising from the unequal spacing of the Landau levels in the nonparabolic conduction band of Bi. The data are satisfactorily interpreted in terms of the ellipsoidal-nonparabolic band-structure model due to Lax. The sharpness of the resonances $\frac{\Delta H}{H}\lesssim 2\%$ makes it possible to re-examine previously reported band-structure parameters of this model.

The polarized Raman spectra of transparent polycrystalline solids are shown to provide results essentially identical to those obtainable from single-crystal Raman studies. Analytic expressions for the polarized scattering functions are obtained and, by way of illustration, are used to determine the symmetries and frequencies of many of the phonon modes for several transparent (Pb, La)(Zr, Ti)${\mathrm{O}}_3$ ceramics in the tetragonal ferroelectric phase.

A study of $\gamma$-ray intensities following neutron capture in ${\mathrm{Mo}}^{92}$ and ${\mathrm{Mo}}^{98}$ provides evidence for a simple reaction mechanism which dominates the decay of the compound nuclear state. The intensities are largely accounted for by the motion of a valency neutron in transitions of the type $p_{\frac{3}{2}}\to d_{\frac{3}{2}}$, $d_{\frac{5}{2}}$, or $s_{\frac{1}{2}}$, and $p_{\frac{1}{2}}\to s_{\frac{1}{2}}$ or $d_{\frac{3}{2}}$.

The (${}_{}{}^3{}_{}{}^{}\mathrm{He},p$) reaction has been studied on all even-even targets from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ to ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. In all cases the $0^{+}\to 0^{+}$ transitions exhibit a characteristic difference from the $0^{+}\to 1^{+}$ transitions. This absence of pure $L=0\mathrm{}$, $0^{+}\to 1^{+}$ transitions can presumably be understood in terms of configuration mixing.

A $T=\frac{1}{2}$ resonance in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been observed in the inelastic scattering of 63.7-MeV $\alpha$ particles by ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. The resonance is centered at 20.4±0.3 MeV excitation and has a width of 3.4±0.4 MeV.

Measurement of the excitation spectra of ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ following the decays of ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ permits the comparison of mirror Gamow-Teller transitions over a wide range of ${W_0}^{+}+{W_0}^{-}$, largely free of uncertainties associated with possible $T_z$ dependencies of nuclear overlap integrals. We find no evidence for second-class currents: Using the conventional parametrization we find that $\left|g_{\mathbf{I}\mathbf{T}}\right|<\mathrm{}7\mathrm{}\times {10}^{-4\mathrm{}}$ at the 99% confidence level as against $g_{\mathbf{I}\mathbf{T}}\approx 2\times {10}^{-3\mathrm{}}$ that comes from the direct comparison of absolute $\mathrm{ft}$ values.

A master equation for the $P$ representation in the Schrödinger picture is derived for a general class of Hamiltonians.

New radar observations yield a more stringent test of the predicted relativistic increase in echo times of radio signals sent from Earth and reflected from Mercury and Venus. These "extra" delays may be characterized by a parameter $\lambda$ which is unity according to general relativity and 0.93 according to recent predictions based on a scalar-tensor theory of gravitation. We find that $\lambda =1.02\mathrm{}$. The formal standard error is 0.02, but because of the possible presence of systematic errors we consider 0.05 to be a more reliable estimate of the uncertainty in the result.