Electronic transfer rates from levels with principal quantum number $p$ from 8 to 14 have been measured in an afterglow helium plasma at electron temperatures from 390 to 2000°K. While the total transfer rates are in satisfactory agreement with both classical and quantum treatments, transitions with $\left|\Delta p\right|>\mathrm{}1\mathrm{}$ are found to have a substantial probability; this favors a classical treatment in this energy range.

With a new method to determine the impact-parameter dependence, $P\left(\rho \right)$, of $K$-shell vacancy production, which utilizes a kinematic analysis of Doppler-broadened x-ray lines, we show that the $K$-shell excitation probability in heavy collision systems at Coulomb barrier energies is both large and narrowly peaked at small impact parameters. In particular, for $1s\sigma$ excitations, $P\left(\rho \simeq 0\right)$ can exceed a few percent with approximately half the total cross section contributed by collisions with $\rho \lesssim 40$ fm.

Experiments using a controlled electron beam interacting with a caviton containing coherent rf fields demonstrate the importance of transit-time damping of localized highfrequency fields. A small transverse magnetic field ($B<~10 \mathrm{G}, \frac{{\omega }_c}{{\omega }_p}<~0.1$) was sufficient to eliminate such transit-time damping. A modulated electron beam is used to demonstrate that the interaction between the beam and the caviton field is phase sensitive. Regeneration of cavitons by streaming particles is discussed.

The superposition of two scattering shells produces beats in the envelope function of the extended x-ray-absorption fine-structure spectrum and a modulation in the scattering phases. From the $k$ values of the extrema in the envelope function and from the inflection points of the phases the separation of these shells can be calculated without knowledge of the scattering phases of the single shells. A resolution in $R$ space up to 0.02 Å can be obtained even in cases where methods used so far are not able to resolve the scattering shells.

Space renormalization group calculations are performed for a class of spin-$S$ Ising systems, using a modification of Migdal's recursion relation. Interface-roughening models are obtained when $S\to \infty$ and tricritical points and critical lines become the roughening temperature and rough phase. The latter corresponds to the low-temperature phases of the classical Coulomb gas and two-dimensional $\mathrm{XY}$ model and implications for the $\mathrm{XY}$-model exponent $\eta$ are discussed.

It is shown that because of a polarization effect the sticking coefficient of atoms on surfaces remains finite down to much lower temperatures than has hitherto been supposed on the basis of the Born approximation to the sticking process.

The thermal conductivity $k$ of $a$-Ge films has been measured between 0.4 and 10 K. The temperature dependence of $k$ shows that heat conduction by phonons is limited by some intrinsic scattering mechanism in addition to boundary scattering. Evidence is presented that these scatterers are localized low-energy excitations which are common in glasses.

Exact solutions for the motion of a particle in a medium with site diagonal and nearest-neighbor off-diagonal dynamic disorder are presented for the first time. Results obtained for the diffusion constant are of relevance to different areas of current interest, such as charge or exciton motion in molecular solids, and motion of light adsorbates on substrates with weak surface potentials.

From a study of $D$ mesons produced in the decay $\psi \mathrm{}\left(3772\right)\mathrm{}\to D\overline{D}$, we have determined the masses of the $D^0$ and $D^{+}$ mesons to be 1863.3±0.9 ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^2$ and 1868.3±0.9 ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^2$, respectively. Under the assumption that the $\psi \mathrm{}\left(3772\right)\mathrm{}$ has a definite isospin and decays only to $D\overline{D}$, the $D^0$ branching fractions to $K^{-}{\pi }^{+}$, ${\overline{K}}^0{\pi }^{+}{\pi }^{-}$, and $K^{-}{\pi }^{+}{\pi }^{-}{\pi }^{+}$ are (2.2±0.6)%, (4.0 ± 1.3)%, and (3.2±1.1)% and the $D^{+}$ branching fractions to ${\overline{K}}^0{\pi }^{+}$ and $K^{-}{\pi }^{+}{\pi }^{+}$ are (1.5±0.6)% and (3.9±1.0)%.

Estimates are presented for the decay of vector mesons composed of heavy quarks into states containing a Higgs boson. If the decays are kinematically allowed, they are probably experimentally accessible when the quark mass $m_q\gtrsim 4$ GeV.

We show that nuclear structure can have a strong effect on the calculated double-charge-exchange cross section. The measured ratio of cross sections at forward angles on an ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ target relative to an ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ target is $R=2.3\mathrm{}\pm 1$. Our calculated value is $R=16\mathrm{}$ with the most simple nuclear model, but a well known, more sophisticated model leads to $R=3\mathrm{}$.

Ultracold-neutron diffraction by a ruled grating was observed. The measured peak positions, linewidths, and intensities agree with expectation. Mirror reflection experiments yielded, for glass, a reflection curve sensitive to surface contamination, and for gold coating, a typical interference pattern.

The x-ray spectra of muonic ${}_{}{}^{186,188,190,192}{}_{}{}^{}\mathrm{Os}$ have been studied at the Clinton P. Anderson Meson Physics Facility. With the use of model-independent methods, precise values of the electromagnetic moments involving the first excited $2^{+}$ state, and in some cases the second excited $2^{+}$ state, have been derived. The results are compared with a calculation using the pairing-plus-quadrupole interaction and indicate a departure from the theoretical predications that had not been evident from previous measurements of lower precision.

We point out the relatively clean geometrical aspect of the Lorentz-Lorenz effect and use it to extract the strength of the effect from an analysis of the elastic scattering of 50-MeV ${\pi }^{+}$ on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. We find that for a finite-range $\pi -N$ interaction there is strong evidence for the effect with a value $0.2<~\xi <~0.6$.

The reaction ($K^{+}, K^{+}p$) is considered as a probe of the deep hole states in nuclei. Distorted-wave impulse-approximation calculations are presented for the knockout of a $1s_{\frac{1}{2}}$ proton from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. We conclude that the experiment should be valuable.

$K$-shell-vacancy production cross sections in Ne→C${\mathrm{H}}_4$, ${\mathrm{N}}_2$, ${\mathrm{O}}_2$, Ne and N→C${\mathrm{H}}_4$, ${\mathrm{N}}_2$, ${\mathrm{O}}_2$, Ne collisions are measured for incident charge states $1^{+}$ to $4^{+}$ and $1^{+}$ to $3^{+}$, respectively, in the projectile energy range 50 to 500 keV. The data indicate there is a real deviation between experiment and the calculations of rotational-coupling cross sections. The data suggest that the deviations are not due to a nonstatistical distribution of the $2p$ vacancies among the $2p\pi$ molecular orbital or a velocity-dependent coupling $N\left(v\right)\mathrm{}$ as has been previously assumed.

We have observed collisional redistribution of laser light scattered by a three-level atom, thallium, in the presence of argon. The two observed spectral components correspond to Raman scattering and collision-induced fluorescence. We have seen the growth of both components from spontaneous to stimulated scattering as the laser intensity is increased. While the gain for the Raman component agrees with theory, the observed gain of the collision-induced fluorescence is over an order of magnitude lower than predicted.

The first observation of optical rotary saturation is reported. Bloch-like equations of motion for rotary saturation are solved by a perturbation calculation and also numerically on a computer. In addition to the rotary-saturation resonance, multiphoton transitions are predicted and observed. A "Debye resonance in the rotating frame" naturally emerges from the equations. The case of two traveling waves interacting with a two-level system is shown to be mathematically equivalent to the rotary-saturation equations.

We speculate on the possibility of liquefying and crystallizing a magnetically confined pure electron plasma.

When the plasma outflow velocity relative to the critical surface is supersonic, compressional density profiles can form in the critical region. These compressions involve dissipative processes like those in collisionless shocks; associated plasma instabilities and reflected ions may inhibit energy transport and enhance laser-light absorption.