Effects of dynamic external pair breaking in superconducting films are studied using microwave reflectivity to probe excess quasiparticle densities. For weak pair breaking, agreement with theory is good, permitting determination of effective quasiparticle recombination times. For strong pair breaking, an expected first-order transition to the normal state is not observed. Instead, a partially dc-resistive state is found in a broad injection region.

Measurements and theoretical estimates are presented of the liquid-gas phase diagram of an electron-hole fluid in pure germanium. The critical point is found to occur in a region where the fluid is an electron-hole plasma at $T_c=6.5\mathrm{}\pm 0.1$ K and $n_c=(8\mathrm{}\pm 2)\times {10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$.

Four distinct EPR spectra observed in ZnSe irradiated by 1.5-MeV electrons at 20.4°K are identified as simple zinc-vacancy, zinc-interstitial close pairs of different microscopic configuration. Correlation of defect alignment with incident-electron-beam direction confirms the identification. Isolated zinc vacancies are also produced but with zero initial production rate, suggesting that their production is a two-step process, the first being the formation of close pairs.

The reaction ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p, n){}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ was studied at $E_p=22.8\mathrm{}$ MeV for both the isobaric-analog-state (IAS) and antianolog-state (AAS) transitions. The difference in the observed angular distributions for these two $L=0\mathrm{}$ transitions is not as striking as in (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $t$) measurements. The strong cancelation expected for the AAS case was observed. The shapes of the angular distributions for both the IAS and AAS were improved by inclusion of a coherent twostep ($p, d$) ($d, n$) process.

The lowest $T=\frac{3}{2}$ level in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Sc}$ is observed as an isospin-forbidden resonance in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(p, p_0){}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at $E_{p,\mathrm{lab}}=4.978\mathrm{}$ MeV with proton partial width ${\Gamma }_p=55\mathrm{}\pm 5$ eV, which is about 50 times smaller than that previously assigned and 6 times smaller than theoretical width estimates. The trend of the proton reduced widths for $T=\frac{3}{2}$ isospin-forbidden resonances obtained from ${\Gamma }_p$ values for target nuclei with $4<~Z<~20$ is shown to be consistent with a $Z^2$ dependence.

A good-resolution study of the reaction ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}(p, t){}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ has revealed the existence of three new $0^{+}$ states in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at 7698, 8284, and 8438 keV excitation. Arguments are presented to show that these states are indeed the long sought-after $0^{+}$, $T=0\mathrm{}$ states with predominantly two-particle, two-hole configurations.

The polarization parameter for the reaction ${\pi }^{-}p\to {\pi }^{0}n$ has been measured at five incident been momenta between 1.03 and GeV/c. The results are compared with predictions of recent phase-shift analyses.

We present the results of a measurement of the $\frac{{K_{\mu 3}}^0}{{K_{e3\mathrm{}}}^0}$ branching ratio, obtained from a study of ${K_L}^0$ decays using a multiwire-proportional-chamber spectrometer. The ${K_{\mu 3}}^0$ and ${K_{e3\mathrm{}}}^0$ events were separated by muon range counters, and ${K_{\pi 3}}^0$ events were separated from the ${K_{e3\mathrm{}}}^0$ sample kinematically. From a sample of approximately 10000 ${K_{\mu 3}}^0$ and ${K_{e3\mathrm{}}}^0$ events, we obtain a value of the branching ratio $\frac{\Gamma \left({K_{\mu 3}}^0\right)}{\Gamma \left({K_{e3\mathrm{}}}^0\right)}=0.662\mathrm{}\pm 0.037$.

We have calculated the value of the Callan-Symanzik $\beta$ function to order $g^5$ for non-Abelian gauge theories with fermions. We discuss internal consistency of the calculation, and consider the approach to the aymptotic energy range in such theories.

If $e^{+}+e^{-}\to \Phi \to \mathrm{hadrons}$, where $\Phi$ is a scalar, radiative beam polarization in storage rings will induce an apparent time dependence of the cross section during an experimental run. This should provide a critical test for models which rely on such a scalar mechanism to enhance the cross section in the present energy range. A model of this kind is presented which identifies $\Phi$ with a composite Higgs field in gauge theories. We check for consistency with other processes and note that there may be an important relation to the shoulder in the dimuon mass distribution in $\mathrm{pp}\to {\mu }^{+}{\mu }^{-}X$.

Quantum-defect methods are used to calculate, by a single unified procedure, the full spectrum of $J=1\mathrm{}$ ${{}_{}{}^1{}_{}{}^{}\Pi _{\mathrm{u}}^{}{}_{}{}^{}}^{-}$ Rydberg levels of ${\mathrm{H}}_2$, extending from the lowest levels of the $2p{\pi }^{-}$ $C{{}_{}{}^1{}_{}{}^{}\Pi _{\mathrm{u}}^{}{}_{}{}^{}}^{-}$ state to the high members of the $\mathrm{np}{\pi }^{-}$ series between the ${{\mathrm{H}}_2}^{+}\mathrm{}(v=0\mathrm{})\mathrm{}$ and ${{\mathrm{H}}_2}^{+}\mathrm{}(v=1\mathrm{})\mathrm{}$ ionization thresholds. Results for the $C$ state are substantially improved over previous calculations based on direct integration of the vibrational Schrödinger equation, while results at higher energies reproduce with high accuracy the recently observed spectrum, including local perturbations.

We show that there exists a strong correlation between the atomic diameter of target metals and their $K^{-}$ mesonic x-ray intensity. The smaller x-ray intensities observed from smaller atoms suggests that the initial capture into large angular momentum states is inhibited in smaller atoms which could be understood if the meson is not localized about a single atom until its kinetic energy is somewhat less than has been presumed. This tendency for mesons to avoid higher angular momentum states when captured by small atoms also explains some previous muonic-atom results.

Resonant enhancement of over 7 orders of magnitude of the two-photon absorption cross section is observed in sodium vapor. Two cw dye-laser beams of different frequencies and propagating in opposite directions are utilized to generate high-resolution spectra which allow the enhancement as well as destructive-interference effects of nearly resonant intermediate states to be clearly demonstrated.

It is suggested that the theory of molecular vibrations, currently based on the harmonic oscillator potential, should be reformulated in terms of the potential $V=K{\left[\frac{(x-x_e)}{x}\right]}^2$. The proposed potential is shown to possess numerous advantages, including an improved physical form, superior eigenfunctions and eigenvalues, the ability to include rotation analytically, and a set of continuum wave functions. The standard classical vibrational analyses are retained.

Sharp structures have been observed in the elastic and vibrational ($v=1\mathrm{}$ and $v=2\mathrm{}$) cross sections of the ground electronic state of CO at energies coincident with the $v=0, 1, \mathrm{and} 2$ levels of the $a{}_{}{}^3{}_{}{}^{}\Pi$ state of CO. The large electric dipole moment of the $a{}_{}{}^3{}_{}{}^{}\Pi$ state of CO (1.38 D) appears to be sufficient to bind temporarily the incoming electron at or near the top of the potential well. The potential energy curve for this "dipole-dominated resonance" coincides with that of the $a{}_{}{}^3{}_{}{}^{}\Pi$ state.

With a relatively simple trial wave function, nontrivial variational bounds are obtained on some transition amplitudes for the $1s$—charge-exchange reaction in the impact-parameter model for ${\mathrm{H}}^{+}$-H scattering. Preliminary results imply that the two-state traveling molecular expansion is superior to the two-state traveling atomic expansion below 25 keV, that the Euler-Lagrange variational method is not necessarily superior to the static method, and that neither is the "best variational method."

We have studied homogeneous nucleation in a binary fluid mixture near the critical point for a temperature range $2\times {10}^{-5\mathrm{}}<\epsilon <2\mathrm{}\times {10}^{-2\mathrm{}}$, where $\epsilon =\frac{(T_c-T)}{T_c}$. We find that the measured degree of critical supercooling is in good agreement with the predictions of a nucleation theory with a nonclassical free energy proposed by Sarkies and Frankel. A slight difference between the temperature dependence of the nucleation curve and that of the coexistence curve is also observed.

We reconsider the flow of a superfluid through the interstices of a porous medium, taking account of the finite volume of the grains and the resulting hydrodynamic drag. A correction factor to the velocity of fourth sound is found, which reconciles a long-standing discrepancy between theory and experiment.

Observations are reported of the ringing of parallel magnetization in superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ when an incremental magnetic field parallel to a steady field is suddenly turned off.

We obtain solutions describing stationary one-dimensional propagation of a coupled nonlinear electron-plasma wave and a nonlinear ion-acoustic wave. These waves have amplitudes linearly proportional to one another, and propagate with approximately the ion-acoustic velocity in the form of periodic wave trains, including solitary waves as a special case.