It is predicted that, for type-II superconductors with $\kappa$ values near $\frac{1}{\sqrt{2}}$ at temperatures below $T_c$, the transition at $H_{c1\mathrm{}}$ is first order when $\frac{{\xi }_0}{l}\lesssim 50$ and the transition at $H_{c2\mathrm{}}$ is first order when $\frac{{\xi }_0}{l}\gtrsim 50$. It may not be possible to observe the latter transition because of experimental difficulties but the former transition should be observable. We also show that the vanishing of the normal-superconducting wall energy is irrelevant for determining if a given superconductor is type I or type II.

The uniform motion of fluxoids in a clean superconductor of extreme type II near zero temperature is discussed on the basis of time-dependent Ginzburg-Landau equations of the diffusion type in a high-field region ($H\simeq H_{c2\mathrm{}}$) and of the wave type in a low-field region ($H\ll H_{c2\mathrm{}}$). In either case the dissipated power in the flux-flow state is found to decrease as the velocity of the fluxoids approaches $v_0=\frac{v_{\mathrm{F}}}{\sqrt{3}}$; while in the low-field case the core energy of a fluxoid in motion assumes a relativistic expression.

It is shown that the Bloch $T^5$ law does not describe the low-temperature electrical resistivity of any metal.

Second-derivative spectra of photoelectron energy distributions from vacuum-cleaved Te were obtained with polarized light of energy 5.2 to 9 eV. Resolution was between 50 and 100 meV using modulation amplitudes up to 1.0 V. Five main structures arise as a result of transitions from the $p$-valence-band triplets, in good agreement with bandstructure calculations. For the first time $d$-conduction-band minima can be located unambiguously at 5.0, 5.6, and 6.3 eV above the valence-band edge.

A new emission band at $h\nu =2\mathrm{}{E}_g$ is observed in Si using carrier injection in a $p-n$ device. The extremly weak photon emission was detected by a special differential counting technique. From the photon energy, the quadratic dependence on the excitation intensity, and the weak temperature dependence, it is concluded that the observed emission is caused by a two-electron transition.

Raman scattering has been studied in the amorphous form of Si and several related, tetrahedrally bonded semiconductors (Ge, GaAs, GaP, InSb). All vibrational modes of the material can take part in the scattering process, and the Raman spectrum is a measure of the density of vibrational states. The amorphous phases are found to have vibrational spectra very similar to the corresponding crystals, reflecting the similarity in short-range order of the two phases.

The observed quantum diffusion of orthohydrogen impurities in solid parahydrogen is interpreted as due to resonant ortho-para conversion. The contribution due to intermolecular interchange is shown to be completely negligible because of "motional narrowing" due to the quadrupolar interaction between the ortho impurities.

The vibrational spectrum for an ${\mathrm{H}}^{-}$ ion on an ${\mathrm{F}}^{-}$ site in Ca${\mathrm{F}}_2$ is that of a perturbed spherical harmonic oscillator. The $\Delta n=1\mathrm{}$ frequencies lie between 928 and 977 ${\mathrm{cm}}^{-1\mathrm{}}$. Tunable C${\mathrm{O}}_2$ lasers have enabled us to study saturation of the single fundamental (0→1) and stepwise excitation to each of the three $n=2\mathrm{}$ levels. A decay-time value $T_1$, based on a crude measurement of the saturation parameter $W$, accounts for the residual linewidth at low temperatures. We discuss "additivity" of stepwise frequencies and polarization "scrambling."

We have generated magnetization in antiferromagnetic Mn${\mathrm{F}}_2$ by selectively pumping the lowest ${}_{}{}^6{}_{}{}^{}A_1^{}{}_{}{}^{}\to {}_{}{}^4{}_{}{}^{}T_1^{}{}_{}{}^{}$ sublattice excitons (or exciton-magnon band) with a pulsed, tunable dye laser. Intersublattice relaxation processes were studied by observing the creation and decay of specific excitations, as induction signals. The exciton relaxation time decreases with increasing temperature and pumping power. We interpret this as intersublattice relaxation assisted by thermally excited magnons.

The shell-model expressions for the partial widths of analog resonances are reformulated to demonstrate that the widths are functions primarily of asymptotic parameters. In particular, it is shown that the widths depend strongly on the asymptotic normalization of the neutron wave function rather than the spectroscopic factor, and that the dependence on the proton potential parameters is, in fact, a dependence on the phase shift.

It is shown that the Faddeev formalism must and can be modified when the short-range two-body behavior is specified by a hard core or boundary-condition model. A new integral equation is formulated for this purpose which, in the special case of boundary-condition model or hard core alone, reduces to an equation in a single vector variable. This feature provides an apparently unique example of a nonseparable interaction for which the three-body equations can be solved exactly.

An upper limit is established on the fraction of energy associated with the gravitational pulses reported by Weber that could be in the form of neutrinos with energies between 0.9 and 100 MeV.

Observations of solar-flare proton fluxes of low energies (1-10 MeV) during the 7 June 1969 event have been used to study the effects of energy-change processes on particles propagating in interplanetary space. It is found that the proton energies are decreasing with time at a rate which is consistent with an exponential-decay time constant of 210±10 h. Since adiabatic deceleration in a uniform solar wind would result in a faster decay (78±4 h), additional processes such as Fermi acceleration or a more general deceleration process must be considered.

Recent observations of the deceleration of low-energy solar cosmic rays in the solar wind are discussed in the context of cosmic-ray transport theory. It is concluded that the rate of deceleration is much slower than would be produced by adiabatic energy change due to the observed expansion of the plasma, so that a competing acceleration process must be operative. Second-order Fermi acceleration by hydromagnetic waves, acting together with adiabatic energy change, is shown to provide a natural interpretation of the observations.

Using fundamental theorems about integral equations, we show that the multiperipheral model for forward pion-pion elastic scattering requires the existence of a Regge trajectory with isospin two.

Inclusive reactions are studied in terms of familiar techniques of Regge phenomenology. Distributions are predicted to approach limiting behavior as $A+B{s}^{\frac{-1\mathrm{}}{2}}$. The constraints of duality and factorization lead to many interesting relations between different single-particle spectra, all of which can be tested at energies below 20 GeV.

Following Mueller, we relate, through a generalized optical theorem, the single-particle production spectrum to a discontinuity in a six-line amplitude. Assuming only analyticity of the six-line amplitude in its angular momenta, we obtain a general expression for the behavior of the production spectrum near the phase-space boundary. To study the asymptotic limit appropriate to this region, we make use of analytic continuation to complex helicities.

The experimentally observed radiation from unstable plasma waves generated by the interaction of an electron beam with a plasma is compared with the longitudinal fluctuation spectrum, determined by incoherent microwave scattering. The results are in agreement with a theory by Ichimaru and Starr for the electromagnetic radiation from anisotropic turbulent plasmas.

We have observed, in cholesteric liquid crystals, optical umklapp processes with which the third-harmonic generation is phase matched. We show that phase-matched third-harmonic generation can be used to measure both the width and the asymmetry of ultrashort pulses.

We investigate the propagation of electrostatic ion waves above the ion cyclotron frequency; we observe resonance effects and enormous wave damping at frequencies near the ion cyclotron harmonics.