This paper reports an analytic estimate of the cross section for the absorption of a $\gamma$-ray photon when the nuclear recoil is compensated by the simultaneous absorption of an optical photon from the radiation field of a high-power laser. A multiphonon transition model is developed and cross sections of the order of 1 ${\mathrm{fm}}^2$ are obtained when nearly resonant intermediate states of nuclear excitation are assumed to lie within a few tens of eV of the transition energy.

The measurement of photons from the quenching of ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$($2S$) state ions produced under special conditions by an rf ion source permit one to deduce a polarizable current of 260 nA, close to 5% of the total ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ current. Zeeman splitting and quenching of unwanted components can be effected at the ion source yielding directly a ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ beam with nuclear polarization.

We report the observation of Fano profiles in the $\pi$-photoionization spectrum of atomic rubidium in the presence of a dc field. Such an observation has been made possible thanks to the use of very high-resolution techniques. It can be considered as an experimental proof of the validity of the "nonhydrogenic" process suggested recently to explain ionization in a static electric field for all atoms except hydrogen.

The lamellar liquid-crystal phase, $L_{\alpha }$, of the potassium-palmitate-water system is shown to be actually polymorphic. Using deuterium magnetic resonance as well as birefringence observations, two sharp phase transitions are observed in the simple neat soap bilayers. Optical conoscopy shows the high-temperature phase to be uniaxial and the other two to be biaxial. Deuteron magnetic resonance shows that each phase transition is accompanied by a change in orientational order.

We investigate the effects of elastic coherency strains in graphite intercalation compounds. The long-range interaction energies of two-dimensional islands of intercalant are calculated. Using the domain model of Daumas and Hérold, we show that these strains drive a mixed-stage or randomly staged crystal to pure-stage ordering.

Pulsed nuclear-quadrupole-resonance (NQR) measurements have been performed in rhombohedral, orthorhombic, and amorphous ($a-$) arsenic. Measurements of $T_1$ provide evidence of low-frequency disorder modes in $a$-As, while the NQR frequencies indicate that the bonding is predominately $p$-like in all three materials. The asymmetric NQR line shape of $a$-As indicates that bond-angle distributions inferred from x-ray scattering and continuous-random-network models do not result primarily from a distribution in bond hydridizations.

Several series of rare-earth compounds have been found to undergo structural phase transitions. For most of them the cause has been the cooperative Jahn-Teller effect. Here we point out that for TmZn and TmCd these transitions are not due to the cooperative Jahn-Teller effect. Rather they are driven by quadrupolar pair interactions. In these systems the lattice follows the quadrupoles and distorts in such a way as to minimize the Jahn-Teller coupling energy.

The observation of band-to-band luminescence from an amorphous solid ($a$-${\mathrm{As}}_2$${\mathrm{S}}_3$) shows the existence of localized states at energies considerably above the mobility edge.

Two new effects associated with Fröhlich sliding-mode conductivity have been observed in Nb${\mathrm{Se}}_3$. First, nonlinear resistance is observed only after a well-defined threshold field is reached. Second, electric fields above the threshold result in noise in the potential difference across a current biased specimen. We interpret the threshold field as direct evidence of charge-density wave depinning and the noise as a result of charge-density wave motion.

Temperature dependence of the quadratic electrogyration coefficient ${\pi }_{13}$ of a nonenantimorphic crystal, ferroelectric K${\mathrm{H}}_2$P${\mathrm{O}}_4$, was successfully measured by using our general method. ${\pi }_{13}$ exhibits an unusual temperature dependence near the transition point. This behavior is primarily similar to that of the electrostrictive coefficient $Q_{13}$ of K${\mathrm{H}}_2$P${\mathrm{O}}_4$. But it reveals the electronic contribution which must be of special interest for elucidating the transition mechanism of the crystal.

Measurements of the $x$ distributions from inclusive ${\nu }_{\mu }$ (${\overline{\nu }}_{\mu }$) reactions are interpreted in the quark-parton model to yield absolutely normalized momentum distributions of valence and sea quarks in the nucleon. The $x$ distributions exhibit a small but significant dependence on energy. From the $y$ distributions we also determine a value of $R=\left[\frac{\int 2x{F}_1\mathrm{}\left(x\right)\mathrm{dx}}{\int F_2\mathrm{}\left(x\right)\mathrm{dx}}\right]-1\mathrm{}$, averaged over the energy interval 20 to 220 GeV.

The angular dependence of proton polarization in $\gamma d\to \mathrm{pn}$ has been measured at photon energies between 400 and 650 MeV. The polarization and differential-cross-section data are consistently explained by introducing a dibaryon resonance $I\left(J^P\right)=0\left(3^{+}\right) or 0\left(1^{+}\right)$ at ≈ 2360 MeV.

The results of an experiment conducted at Fermilab to measure the polarization of the final-state proton in the reaction $p+p\to p_{\uparrow }+X$ and $p+\mathrm{C}\to p_{\uparrow }+X$ are presented. Measurements were made at beam energies of 100, 200, 300, and 400 GeV for $P_T$ from 0.5 to 1.5 GeV/c and $x_{\mathrm{F}}$ between - 0.7 and - 0.9.

The ratio $R_2\left({}_{}{}^3{}_{}{}^{}\mathrm{H}\right)$ of the $D$- and $S$-state asymptotic normalizations of the neutron-deuteron tail of the triton wave function is calculated from a solution of the Faddeev equations with the Reid soft-core potential. We find $R_2\left({}_{}{}^3{}_{}{}^{}\mathrm{H}\right)=-0.24\mathrm{}$ ${\mathrm{fm}}^2$. Both the phase and magnitude of the calculated ratio are in agreement with the experimental value determined from the recent measurements of tensor analyzing powers for ($d$,$t$) reactions. An estimate of $R_2$ for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ with a Coulomb correction gives $R_2\left({}_{}{}^3{}_{}{}^{}\mathrm{He}\right)\approx -0.24\mathrm{}$ ${\mathrm{fm}}^2$.

Implications of the most recent pion-production data are discussed. It is observed that they can be used to answer some of the crucial questions raised in understanding the basic reaction mechanism of relativistic heavy-ion collisions. As a by-product of this discussion, it is shown that the volume of the pion sources in violent collisions can be determined from single-particle inclusive data. Further hadron-nucleus and nucleus-nucleus collision experiments are suggested.

The elastic small-angle scattering of 15- to 25-keV electrons by He, Ne, and Ar shows a rapid increase towards decreasing scattering angles superimposed with a diffraction pattern. The observed excess of the elastic differential cross section as compared with the Born cross section is due to the coupling to the inelastic channels. It may be also explained as a diffraction into the shadow of the inelastic scattering which dominates the forward direction.

A kinetic description is presented of ponderomotive effects which originate from a time-dependent high-frequency (hf) field. The solution of the corresponding generalized diffusion equation shows the appearance of a nonlocal term which reflects a memory of the plasma. It leads to significant changes of the plasma properties during and after the duration of the hf field. The plasma is irreversibly heated and a region of high density and high temperature appears at the center of hf activity in the time asymptotic limit.

A Maxwellian velocity distribution with cold and hot electrons causes the electron heat conductivity associated with the cold component ($\nabla T_c$) to decrease and even change sign in a weak magnetic field or parallel to a strong magnetic field. The same occurs transverse to a strong magnetic field and to $\nabla T_c$ but not parallel to $\nabla T_c$. Nonetheless, the total heat flow retains its proper sign as a result of new contributions from $\nabla n_c$ and possibly $\nabla T_h$. Various transport properties and the self-generated magnetic field are also analyzed.

A new fundamental radiation-induced defect in high-purity synthetic silica has been identified by electron-spin-resonance studies of ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$-enriched Si${\mathrm{O}}_2$ as a peroxy radical ${\mathrm{O}}_2^{-}$ bonded to one Si in the glass matrix. The precursors of these defects are envisioned to be ≡ Si-O-O-Si ≡ structures, some of which preexist in the silica, are formed in greater numbers during neutron bombardment, and which may release an electron either during irradiation or subsequent annealing.

The first low-energy-electron-diffraction measurements using a polarized incident electron beam are reported and compared to measurements where an unpolarized incident beam is analyzed after scattering. Whereas, because of multiple scattering, equivalence of the two measurements is not expected in general, excellent agreement is obtained for specular scattering in the (010) plane from W(100). A theoretical argument is presented for the case where the scattering plane is a mirror-symmetry plane of the crystal.