The relative absence of ν${\mathrm{¯}}_{\mathrm{\mu }}$-induced charged current events with respect to ${\nu }_{\mathrm{\mu }}$-induced events at large (>0.45) and large y (>0.70) enables us to limit the right handed coupling of the weak current. Our data restrict ‖η${\mathrm{\Vert }}^2$=‖${\mathit{g}}_{\mathit{R}}$/${\mathit{g}}_{\mathit{L}}$${\mathrm{\Vert }}^2$<0.0 015 with 90% C.L. Within the framework of left-right symmetric models, this measurement imposes a limit upon the mixing angle of the left and right handed bosons. Unlike the limits imposed by the μ-decay and nuclear β-decay experiments, our limit is valid irrespective of the mass of the right handed neutrino.

For each of several proposed π-meson cutoff masses (${\mathrm{\Lambda }}_{\mathrm{\pi }}$) in the πNN form factor, we obtained ρ-meson cutoff mass (${\mathrm{\Lambda }}_{\mathrm{\rho }}$) in the ρNN form factor so that the three-body force with these form factors may reproduce the triton binding energy. We calculated the wave function and the exchange current in the Gamow-Teller matrix element for the triton beta decay, consistently using these form factors. The most favorable set ${\mathrm{\Lambda }}_{\mathrm{\pi }}$=0.81 GeV and ${\mathrm{\Lambda }}_{\mathrm{\rho }}$=1.13 GeV yielded a triton binding energy of 8.485 MeV (experimentally, 8.482 MeV) and a Gamow-Teller matrix element divided by √3 0f 0.955 (experimentally, 0.961).

Polarization asymmetries observed in elastic tagged photon scattering at excitations between 16 and 30 MeV were used to identify the isovector giant electric quadrupole resonance in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ through its interference with underlying electric dipole strength. Resonance parameters reflecting the distribution of E2 (T=1) transition strength were extracted in a manner that has minimal sensitivity to uncertaintities in the Delbruck amplitudes or in the q dependence of the modified Thomson amplitudes. The isovector E2 resonance was found at an excitation of 20.2±0.5 MeV, with a width of 5.5±0.5 MeV, and a strength corresponding to 1.4±0.3 times the isovector quadrupole sum rule.

A two-degrees-of-freedom Hamiltonian system is constructed and serves as a toy model for compound-nucleus scattering. The model contains both direct reactions and isolated and/or overlapping resonances. All its properties are in good agreement with the random matrix theory of compound-nucleus reactions. We attribute this agreement to the chaotic character of the process and its universality.

In microwave multiphoton transitions between Rydberg atoms driven by short microwave pulses we have observed that the rise and fall of the pulse are as important as the peak and together can produce readily visible interference in the transition probability. Furthermore, the transition probability vanishes for some tunings and can be suppressed if the ac Stark shift brings the two states into resonance at the peak of the microwave pulse with a large Rabi frequency.

We present an experimental investigation for chlorine molecules and their atomic fragments in which high field molecular dissociation is followed by fragment ionization. It is shown that the intensity dependence of the photoelectron and atomic photofragment energy spectra provides a direct measure of the fragments’ ac-Stark shift. Furthermore, we observe an unusually strong above-threshold ionization photoelectron series associated with the two-photon ionization of the excited chlorine fragment. This implies that the fragments are experiencing field strengths in excess of the ‘‘low field’’ saturation. These results are compared to a single-channel quantum-defect calculation.

We present a remarkable analytic result which suggests that a continuum can be used as an intermediary for a significant transfer of population from one discrete state to another discrete state in a stimulated Raman transition. The population transfer is accomplished by employing two laser pulses that overlap in time, arranged in the so-called counterintuitive order. That a continuum can be used for population transfer is shown here for the first time. It promises to open up more channels for selective coherent excitation of atoms or molecules.

The photoionization process NO ${\mathit{A}}^2$${\mathrm{\Sigma }}^{+}$(v=0, N=22)→${\mathrm{NO}}^{+}$ ${\mathrm{X}}^1$${\mathrm{\Sigma }}^{+}$(${\mathit{v}}^{+}$=0, ${\mathit{N}}^{+}$)+${\mathit{e}}^{\mathrm{-}}$ is studied with sufficient energy resolution that the photoelectron angular distributions associated with individual rotational levels ${\mathit{N}}^{+}$ of the ion are determined. By ionizing with left and right circularly polarized light and observing the change in the rotationally resolved photoelectron angular distributions, we can deduce all dynamical information, including the signs of the relative phase shifts of the photoelectron partial waves. This information constitutes the first complete description of the photoionization of a molecule.

We have measured the absorption line shape for two-photon absorption from a broadband field known as the real Gaussian field. We observe that, in the case of large optical bandwidth, the width of the absorption spectrum is narrower than that of the optical field. Agreement with calculated line shapes and widths is excellent.

We present calculated optical harmonic spectra for atoms and ions in the high intensity regime to current short-pulse experiments. We find that ions can produce harmonics comparable in strength to those obtained from neutrals, and that the emission extends to much higher order. Simple scaling laws for the strength of the harmonic emission and the maximum observable harmonic are suggested. These results imply that the photoemission observed in recent experiments in helium and neon contains contributions from ions as well as neutrals.

A free-electron laser operating in the gain-focusing regime is discussed. The variation of growth rate, radius of curvature of wave fronts, filling factor and efficiency with emittance, and energy spread is derived. The reults, which are based on the Vlasov-Maxwell system of equations, are obtained by minimizing a variational functional. When plotted as a function of emittance, the efficiency at maximum growth rate peaks at a nonzero value of emittance. For small values of energy spread, the efficiency at maximum growth rate increases with energy spread, in contrast to intuitive expectations.

We present the first experimental demonstration of phase locking between successive optical micropulses in a free-electron laser in which the electron pulses are separated by a fraction of the optical-cavity round-trip time. A Fox-Smith interferometer arrangement has been used to induce a high degree of interpulse phase coherence. Surprisingly, a substantial amount of coherence has also been observed without the phase-locking arrangement. A tentative explanation of this phenomenon is given.

We report on experimental observations of spatial modifications, induced by the Kerr effect, in the profile of a weak probe beam due to a cross-phase modulation from a strong pump beam. The measurements were performed in a self-defocusing nonlinear medium (semiconductor doped glass) where the observation of induced focusing and spatial modulation instability were made possible. The experimental results are in good agreement with numerical simulations.

We analyze line measurements of turbulent shear stress in a turbulent boundary layer in terms of isoshear contours. The statistics of the relative location of contour center lines points to a relation with coherent structures. The shape of these contours exhibits a remarkable scaling behavior that is reminiscent of that found in spatiotemporal chaos.

We propose a simple ansatz that relates the diffusion propagator for the molecules of a fluid confined in a porous medium to the pore-space structure factor. Theoretical arguments and numerical simulations show that it works well for both periodic and disordered geometries. The ansatz allows us to deconvolve structural data from momentum dependent pulsed field gradient spin-echo data.

Pressure driven currents are observed in an electron cyclotron resonance (ECR) heated, small-aspect-ratio toroidal plasma in the CDX-U device. A toroidal current of 1.05 kA was generated with ∼8 kW of ECR power. At this current level, the poloidal field created by these currents is significantly larger than the vacuum field and produces closed flux surfaces in a small-aspect-ratio tokamak geometry. After flux surface formation we hypothesize that bootstrap currents are driven to maintain the discharge. This internally driven current may offer an attractive method to start up and maintain the tokamak discharge.

Various nonlinear scenarios are given for the evolution of energetic particles that are slowing down in a plasma and simultaneously excite the background plasma waves. Depending on the relationships between the source, the background damping, and the classical transport rate, either a steady state or pulsations arise. At the predicted saturation levels, anomalous particle transport is rather low. However, if the particle orbits are stochastic at the amplitude level needed to balance the growth rate with the wave trapping frequency, a phase space ‘‘explosion’’ occurs, giving enhanced transport.

The first measurements of the line-integrated electron density in a coaxial microsecond-conduction-time plasma opening switch during switch operation are presented. Current conduction is observed to cause a radial redistribution of the switch plasma, with a large decrease in axial line density over most of the radial extent of the switch. A local reduction in line density of more than an order of magnitude occurs by the time opening begins. It is hypothesized that this density reduction allows the switch to open by an erosion mechanism. Initial numerical modeling efforts have reproduced the principal observed results.

The solution to the Pauli spinor equation for a neutral magnetic dipole in a periodic magnetic field gives rise to an energy band structure as a consequence of Bloch’s theorem. Since the two spin components see differing potentials, it is possible to arrange the magnetic field so that only the kinetic energy corresponding to one spin component is in a band while that of the other is in a band gap. Only one component from an incident beam would propagate through the oscillating field while the other would be completely reflected. Hence, a very efficient polarizing filter is obtained.

Quasielastic light-scattering measurements are reported for a chiral smectic-C material as a function of enantiomer concentration and applied electric field. The elastic constant ${\mathit{B}}_1$ and associated viscosity have been determined. More importantly, it was found that ${\mathit{B}}_1$ is composed of a bare part ${\mathit{B}}_1^0$ and a polarization-dependent part ∝${\mathit{P}}_0^2$/${\mathit{q}}^2$. For q<${10}^5$ ${\mathrm{cm}}^{\mathrm{-}1}$, the polarization-dependent term is much larger than ${\mathit{B}}_1^0$.