We have observed events of the type ${\mu }^{\pm }+{\left(3\mathrm{}\pi \right)}^{\mp }$ in $e^{+}{e}^{-}$ interactions at center-of-mass energies above 6 GeV. The properties of the events are consistent with their coming from the heavy-lepton decays $\tau \to \mu \nu \overline{\nu }$ and $\overline{\tau }\to \overline{\nu }3\pi$ or $\overline{\tau }\to \overline{\nu }4\pi$. The three-charged-pion invariant-mass distribution shows a significant peak at a mass 1.1 GeV/${\mathit{c}}^2$. We find the branching ratio into three charged and any number of neutral pions $B({\tau }^{+}\to \overline{\nu }{\pi }^{+}{\pi }^{+}{\pi }^{-}n{\pi }^0)=0.18\mathrm{}\pm 0.065$.

A simple dynamical model is shown to reproduce heavy-ion fusion excitation functions over a wide mass and energy range. The trajectory calculations employ the proximity nuclear potential and the proximity one-body nuclear friction. The importance of tangential friction in determining the magnitude and shape of the fusion excitation functions at higher energies is discussed.

States at 6.42-, 6.75-, and 7.06-MeV excitation have been observed in electron scattering on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The transverse character of the excitation cross section has been established. The states have been interpreted as the $\nu {\left({i_{\frac{13}{2}}}^{-1\mathrm{}}{j}_{\frac{15}{2}}\right)}_{{12}^{-},{14}^{-}}$ and the $\pi {\left(h_{\frac{11}{2}}{}_{}{}^{-1\mathrm{}}{}_{}{}^{}i_{\frac{13}{2}}^{}{}_{}{}^{}\right)}_{{12}^{-}}$ single-particle hole excitations of the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ ground state, on the basis of the measured momentum-transfer dependence and the magnitude of the cross section.

We calculate the coupling constants $C^2({}_{}{}^3{}_{}{}^{}\mathrm{H}-Nd)$ and $C^2({}_{}{}^3{}_{}{}^{}\mathrm{H}-N{d}^{*})$ by a simple method recently proposed to simulate three-body vertices through spectator functions which require effective two-body normalization. The values obtained (3.2 and 4.8) are in good agreement with the recent determinations of these quantities by Plattner et al. from $p+d$ and $p$+${}_{}{}^3{}_{}{}^{}\mathrm{He}$ scattering data.

The impact-parameter dependence of Ar $K$ x-ray excitation in 2.5-, 4.5-, and 8-MeV Ar-Ar collisions has been measured in a photon-scattered-ion coincidence experiment. The excitation probability has been found to increase sharply at small impact parameters; this effect cannot be explained by current theoretical models.

A new method is proposed for collectively accelerating bunches of ions with an intense relativistic-electron beam. By varying the beam energy in time, acceleration of a slow Doppler-shifted cyclotron wave can be accomplished, without accompanying degradation of the beam equilibrium. Test-particle calculations employing this acceleration scheme indicate performance which is highly competitive with other collective-ion-acceleration mechanisms.

Stabilization of drift waves by external rf fields at frequencies near the lower-hybrid frequency has been observed experimentally in a $Q$ machine in the collisionless regime with ${\left(\frac{{\omega }_{\mathrm{pe}}}{{\omega }_{\mathrm{ce}}}\right)}^2\ll 1$. Stabilization is due to a resonant ponderomotive force which increases the drift frequency, thus enhancing the electron Landau damping. The observations are in general accord with analyses in the literature when finite-geometry effects appropriate to the present experiment are taken into account.

We examine how internal fields affect orientational energies in superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. We find that the orientational effect of a magnetic field due to the interaction between magnetic dipole moments is increased modestly, but that the analogous effect due to the interaction between electric dipole moments induced by an external electric field is suppressed significantly. Our estimated of the electric fields required to produce orientational effects are at least an order of magnitude larger than previous ones.

Diffraction of helium atoms at a clear Si(100) surface has been observed. Integral-order, half-order, and quarter-order peaks consistent with the two-domain $c(4\mathrm{}\times 2)$ surface reconstruction have been recorded. Additional peaks at the ($\frac{\overline{1}}{2}\frac{\overline{1}}{2}$) and ($\frac{\overline{3}}{2}\frac{\overline{3}}{2}$) positions are also seen. The diffraction intensities amount to ∼${10}^{-3\mathrm{}}$ of the incident beam. The major portion of the scattering is spread over a large range of solid angle with broad maxima characteristic of rainbow scattering.

Saturation measurements of magnetoabsorption in $n$-InSb have shown that electron-electron scattering determines the electronic lifetime in the first Landau level, giving values of ∼${10}^{-10\mathrm{}}$ sec for excited electronic densities of ${10}^{13}$ ${\mathrm{cm}}^{-3\mathrm{}}$. Lifetimes in impurity levels are ∼${10}^{-7\mathrm{}}$ sec determined by acoustic phonon scattering.

We show that observed changes in the nature of the conducting state of $1T$-Ti${\mathrm{Se}}_2$ in going from the normal semimetallic state to the charge-density-wave semiconducting state can be successfully modeled by variation of a single structural parameter, $z$, which modulates the Ti-Se bond length. These ab initio band-structure results lead to a number of interesting experimental consequences.

I show that the equality of the rates for $\tau \to {\mu }^{+}+\mathrm{neutrinos}$ and ${\tau }^{+}\to e^{+}+\mathrm{neutrinos}$ does not necessarily exclude the possibility that ${\tau }^{+}$ is a paraelectron with the same lepton number as $e^{-}$, but it does require some rather unconventional decay matrix element. Different matrix elements predict different values for Michel $\rho$ parameters and daughter lepton helicities; tests for the paraelectron assignment occur in $e^{+}{e}^{-}$ annihilation.

The $n=2, 4, 6$ moments of the nucleon structure function $F_2$ were evaluated from muon and electron deep-inelastic scattering measurements on hydrogen and deuterium done at Stanford Linear Accelerator Center and Fermilab. From these moments the quark and gluon content of the nucleon was determined by application of the theory of asymptotic freedom. With the values ${0.25}_{+0.10\mathrm{}}^{-0.11\mathrm{}}$ for $R=\frac{{\sigma }_L}{{\sigma }_T}$, the scale parameter of the theory was determined to be $\Lambda =600\mathrm{}\pm 80$ MeV.

Existing data for $1g_{\frac{9}{2}}$ nucleon-transfer reactions on Sr isotopes are analyzed using root-mean-square radii which were recently obtained from the analysis of large-angle electron scattering. The present analysis implies values of rms radii for $1g_{\frac{9}{2}}$ single-particle orbits which agree with those obtained from electron scattering and disagree with predictions of Hartree-Fock calculations.

A new strength function continuous in energy and a smoothing parameter is constructed which arbitrarily closely approximates the discontinuous strength function for line broadening defined by Lane. The functional form of the Lane strength function is then derived for a fragmented isobaric analog resonance. Its non-Lorentzian form is explicitly and qualitatively different from that assumed in a recent analysis of isobaric analog resonances.

We formulate an extended time-dependent Hartree-Fock approximation which includes particle collisions. As the configuration-space analog of the quantum Boltzmann equation, it can be utilized to study the dynamics of nuclear or other fermion systems when irreversible dissipation is present.

Reactions of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ have been used to produce ${}_{}{}^{194}{}_{}{}^{}\mathrm{Hg}$ compound nuclei at excitation energies of 98 and 142 MeV. This combination of entrance channels permits the separation of energy and spin effects on the exit channels. Fission probability clearly increases with angular momentum at fixed energy. However, there is no increase in the cumulative fission fraction from 98 to 142 MeV for essentially constant spin domain. In contrast the probability of ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ evaporation increases rapidly with energy and seems to shield the system from fission.

Measured cross sections for the breakup of ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ ions in the Coulomb field are found to be in disagreement with calculations based on a model which describes well the Coulomb breakup of deuterons. A possible explanation for this discrepancy in terms of Coulomb excitation of the projectile is suggested.

Linear, Doppler-free laser spectroscopy is applied to atoms or molecules having metastable states. A tightly collimated beam of metastables is crossed with a tunable-dye-laser beam. Absorption of light quenches the metastables beam. The method has been used to resolve and measure, for the first time, the fine structure of the $3s, 3d:{}_{}{}^3{}_{}{}^{}\Sigma , {}_{}{}^3{}_{}{}^{}\Pi , {}_{}{}^3{}_{}{}^{}\Delta$ complex of the hydrogen molecule. Isotope shifts have been measured in atomic neon. A discussion is given of the possibility of increasing the precision in the measurement of the Rydberg constant.

We present an experimental survey of a group of Rydberg states of sodium in magnetic fields up to 6 T, where levels from different terms overlap and interact strongly. The observed energy levels and relative line intensities for even-parity $m_l=1\mathrm{}$ terms in the vicinity $n=28\mathrm{}$ are in good agreement with calculations based on a numerical diagonalization using spherical basis states in the range $n=25-31\mathrm{}$.