This paper discusses a method for the extraction of the ratio $f_s=\frac{\int \mathrm{xs}\left(d\right)\mathrm{dx}}{\int \mathrm{xd}\left(x\right)\mathrm{dx}}$ from dimuon rate measurements in neutrino and antineutrino scattering, which takes into account the threshold effects for heavy-quark production. From the $y$ dependence of $\overline{\nu }$ scattering to dimuon final states the parameter ${m_c}^2$, which appears in the definition of the slow rescaling variable $\xi =x+\frac{{m_c}^2}{2E{M}_{p}y}$, is estimated. This paper further discusses the crucial uncertainties inherent in the measurement of $f_s$.

Predictions of the Paris potential for the analyzing power in $\mathrm{pp}$ scattering at low energies are compared with recent high-precision measurements at 6.141 MeV and earlier measurements at 10 and 16 MeV. Phase-shift values are also presented and discussed in view of previous analyses.

The proton yields from the interaction of pions on nuclear targets with $12<~A<~181$ were measured in the region of the $\Delta (3, 3)$ resonance. The shift in proton energies with angle is analyzed in terms of the average number of nucleons that have participated in absorbing the pion's momentum and total energy. The effective number of interacting nucleons, for both ${\pi }^{+}$ and ${\pi }^{-}$ incident, is found to be ∼ 3 for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and increasing to ∼ 5.5 for ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$. These effective numbers of nucleons are also consistent with the ratio of proton yields from ${\pi }^{+}$- and ${\pi }^{-}$-induced reactions.

Results of exact finite-range distorted-wave Born-approximation calculations are presented for the reactions ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}(p, t){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}(t, p){}_{}{}^{50}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(t, p){}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$. The calculations employ a realistic triton wave function, and realistic nuclear-structure overlap functions. The theoretical cross sections are in good agreement with experiment which-implies that the distorted-wave Born approximation provides a satisfactory description of these reactions without recourse to higher-order reaction mechanisms.

The elastic-photon-scattering cross section for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been measured at 90° and 135° in the energy range from 23.5 to 39 MeV. These data disagree with the predicted scattering, derived from the measured photonuclear absorption cross section, if only $E1\mathrm{}$ transitions are assumed. To explain the difference in these cross sections, a large component of electric quadrupole absorption between 24 and 40 MeV is inferred.

The Pauli principle is introduced into the theory of the optical potential in a consistent manner. This is facilitated by an appropriate choice of off-shell extension for the two-fragment transition operators. Dynamical equations for the optical potential are derived and low-order approximations are discussed.

Cross sections for electron loss from excited hydrogen atoms in collision with a ${\mathrm{N}}^{3+}$ beam at 40-keV/amu collision energy were determined by use of a crossed-beams experiment. The value of the principal quantum number, $n$, of the excited atoms investigated ranged from 9 to 24. In this range the electron-loss cross section increases as $\sim n^3$, in contrast to the $n^2$ increase predicted by a number of theories.

The initial product vibrational-state distribution is obtained for the thermal associative-detachment reaction, ${\mathrm{Cl}}^{-}+\mathrm{H}\to \mathrm{HCl}(v=0, 1, 2)+e$, produced by infrared chemiluminescence in a flowing afterglow. The ratio of $\mathrm{HCl}\mathrm{}(v=2\mathrm{})\mathrm{}$ to $\mathrm{HCl}\mathrm{}(v=1\mathrm{})\mathrm{}$ population formed in the reaction is $\frac{N_{v=2\mathrm{}}}{N_{v=1\mathrm{}}}=0.60\mathrm{}\pm 0.03$. Comparison of the total emission intensity to that from a reaction of similar exothermicity suggests that $\mathrm{HCl}\mathrm{}(v=0\mathrm{})\mathrm{}$ formation may be small.

It is shown that, because of currents in molecules, the Hellmann-Feynman theorem fails at 10-ppm accuracy. The general non-quantum-electrodynamic form of the additional dynamic forces is rigorously derived and applied. The first-order perturbation-theoretical correction to the 1-0 vibrational transition energy for the ground electronic state of H${\mathrm{D}}^{+}$ is calculated. The value obtained, -0.072 ${\mathrm{cm}}^{-1\mathrm{}}$, agrees with the extant experimental minus theoretical energy difference, -0.07 ${\mathrm{cm}}^{-1\mathrm{}}$.

The principle of bistable operation with two independent input optical beams is presented; the nonlinear medium inside a Fabry-Perot resonator is in two-photon resonance with the beams. The transmission characteristics of the bistable device are derived in both the absorptive and the dispersive regimes. The degenerate case, and the effect of a new parameter associated with the optical Stark shift in a two-photon process, are also discussed.

Self-induced transparency has been observed for the degenerate, $F=3\mathrm{}\to 4$, hyperfine component of the 1.315-μm magnetic dipole transition of atomic iodine, at high optical power levels, up to 50 MW ${\mathrm{cm}}^{-2\mathrm{}}$. For pulse areas approaching $2\pi$, the dynamics of the strong coherent resonant self-focusing which accompanies self-induced transparency have been studied with a streak camera to provide time-dependent analysis of the spatial beam profile.

The radial penetration of low-frequency ($\omega \ll {\omega }_{\mathrm{pe}}$) electromagnetic fields is measured in cylindrical geometry. Classical skin depths ($\frac{c}{{\omega }_{\mathrm{pe}}}$) are observed until the wave frequency is low enough for electron thermal effects to result in enhanced wave penetration.

The process of coalescence of magnetic islands is investigated. For intermediate values of the resistivity $\eta$, the reconnection rate $M_s$ is independent of $\eta$, although the reconnection process is basically different from a Petschek-type model. For very small values of $\eta$ the dynamics of the coalescence process is more complex with reconnection being significantly slower.

Argon-filled plastic-coated glass shells were imploded with the six-beam ZETA laser system with short (∼50-psec) pulses of energy ∼ 100 J. Densities in the range 4-6 g/${\mathrm{cm}}^3$ [$N_e=(1.0-0.5)\mathrm{}\times {10}^{24}$ ${\mathrm{cm}}^{-3\mathrm{}}$] temperatures ∼ 1 keV were deduced from the Stark profiles of various ${\mathrm{Ar}}^{16+}$, ${\mathrm{Ar}}^{17+}$ x-ray lines. These densities are achieved because of the shell thickness and radiational cooling of the high-$Z$ fill gas and show that symmetric illumination can lead to high-volume convergence (> 1000).

The specific heat of liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been measured from 1 to 10 mK between 0 and 32.5 bars. The values implied for the effective mass are considerably smaller than the currently accepted ones. Near zero pressure the specific-heat jump is close to the BCS value 1.43, and at 32.5 bars it has reached 1.90 in the $B$ phase and 2.04 in the $A$ phase. The temperature dependence of the specific heat in the $B$ phase agrees with a model of Serene and Rainer. The latent heat at the $A-B$ transition has been measured.

Sharp lines in the bremsstrahlung spectrum have been observed for 1.5-4-MeV electrons channeled along a $〈111〉$ direction in silicon. The lines originate in transitions between bound states in the axial transverse potential and may be described as characteristic radiation from a two-dimensional atomlike system moving with relativistic velocity in the $〈111〉$ direction.

A real-space dynamic renormalization-group scheme is used to evaluate static and dynamic correlation functions for a kinetic Ising model on a two-dimensional square lattice. The critical exponents obtained from the correlation functions calculated using this method satisfy the proper static and dynamic scaling relations and are in excellent agreement with known values.

This paper reports a new photoluminescence (PL) band in indirect $\mathrm{Ga}{\mathrm{As}}_{1-x}{\mathrm{P}}_x$ that lies between donor-bound and free exciton PL peaks. It has relatively strong $X$-point phonon sidebands and an asymmetric shape with an abrupt high-energy cutoff. The lifetime varies rapidly over the PL linewidth. Properties of excitons in fluctuating random-alloy potentials are discussed. It is suggested that this line is due to excitons trapped by such potentials.

This Letter reports on the $\mathrm{KLL}$ Auger spectra of Na and Mg excited with different x-ray sources. Intrinsic plasmon creation in x-ray photoemission leads to plasmongain satellites in the Auger process. With low-energy x rays the probability of intrinsic plasmon creation in x-ray photoemission and hence the plasmon-gain probability is reduced. With high-energy x rays the plasmon-gain intensities agree with predictions of a new formalism of photoemission and Auger transitions as a single quantum mechanical process.

Molecular-dynamics calculations on melting and evaporation in a two-dimensional (2D) Lennard-Jones system show a nonuniform particle distribution in the temperature and density intervals where the phase transitions take place. The behavior of the system agrees qualitatively with the behavior of a corresponding 3D system with a liquid-gas critical point and first-order phase transitions. No evidence is found for the two-stage melting behavior which has recently been predicted.