Unlike prior attempts to describe the motion of electronic charge carriers in disordered materials, we suggest that the (holelike) charge carriers may actually be selftrapped, i.e., small polarons. In support of our hypothesis, we discuss our measurements of the electrical conductivity, thermoelectric power, and Hall mobility on some chalcogenide glasses.

The phonon scattering by shallow acceptors in Si has been observed to decrease rapidly with magnetic field at high fields and low temperatures. This is the behavior expected for the ground-state quartet of the undistorted site. The scattering by shallow acceptors in Ge is, however, almost independent of field, indicating a quite different ground-state structure. This is believed to be the result of a dynamic Jahn-Teller distortion.

We present theory $a$ of structural phase transitions in which the lowering of symmetry originates from a Jahn-Teller effect of the ionic constituents with electronic $E$-type doublets. We consider a model in which the three lowest vibronic states of the Jahn-Teller complexes are well separated from the higher excitations. The static and dynamic properties are studied in an $S=1\mathrm{}$ pseudospin representation.

The first eight terms of the low-field, high-temperature staggered-susceptibility series are obtained for a two-sublattice exchange-interaction model of antiferromagnetism for arbitrary spin and loose-packed lattices. For the bcc lattice and $S=\frac{1}{2}$ (Heisenberg model) the ratio of the antiferromagnetic critical (Néel) temperature $T_{\mathrm{N}}$ to the ferromagnetic critical (Curie) temperature $T_c$ is 1.09 ± 0.01, and the antiferromagnetic susceptibility critical index ${\gamma }_{\mathrm{N}}$ is ${1.40}_{-0.02\mathrm{}}^{+0.03\mathrm{}}$.

Measurements on two-spin fluctuation light scattering in Mn${\mathrm{F}}_2$ have been obtained over the temperature range 2-300°K; the results are in good agreement with a theoretical analysis based on frequency moments and intensity of the scattering spectra. We find that the first moment shows critical-type behavior in the vicinity of the Néel temperature $T_{\mathrm{N}}$ and that the measured high-temperature second moment allows a determination of the antiferromagnetic exchange constant in the paramagnetic phase.

With the use of the cranking formula, the coordinate-dependent mass parameters of the kinetic-energy operator in fission processes and heavy-ion collisions are calculated in the two-center oscillator model. It is shown that the reduced mass and also the classical moment of inertia are obtained for large separations of the fragments. For small separations, however, the mass parameter for the motion of the centers of mass of the fragments is larger than the reduced mass by an order of magnitude.

In addition to the quartet excitations between major oscillator shells (intershell quartet states), we propose quartet excitations within a shell (intrashell quartet states). A phenomenological quartet shell model is devised to predict the energies of these states. Evidence for such excitations is also found in a microscopic multiconfiguration Hartree-Fock calculation.

A method for resolving the giant resonance excitation into its isospin components is applied to several nuclei. The relative strengths of the different isospin channels and their energy splittings are calculated. Consistency is found with the existence of the neutron "halo" in heavy nuclei.

The ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , p){}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , n){}_{}{}^3{}_{}{}^{}\mathrm{He}$ cross sections have been determined with a magnetic spectrometer in the energy interval of 30.0 to 51.8 MeV. We find that the average value of $\frac{\sigma (\gamma , p)}{\sigma (\gamma , n)}$ is 1.03±0.04 in the above energy interval. The ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , p)$ cross section decreases from 1.52±0.13 mb at 31.7 MeV to 0.36±0.03 mb at 51.8 MeV.

The two-neutron transfer reaction (${\mathrm{O}}^{18}$, ${\mathrm{O}}^{16}$) to the ground and first $2^{+}$ states of ${}_{}{}^{94,96,98,100}{}_{}{}^{}\mathrm{Mo}$ has been measured at 55-, 60-, 70-, and 77-MeV projectile energy. Angular distributions and absolute cross sections are compared with the theory of Dar, which accounts for a large part of the variation of cross section with target mass number, energy, and the observed angular distributions. Evidence for multiple processes is exhibited in the excited-state cross sections.

A continuum shell-model calculation based on the collective correlation model has been made for the giant resonance of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ using the eigenchannel reaction theory. The low-lying negative-parity states of ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ have been taken into account by corehole coupling. Partial, total, and integrated photoabsorption cross sections are calculated for the region of the giant dipole resonance.

It is shown that the Gribov-Migdal lower bound on the magnitude of the two-Pomeranchukon cut is not valid unless both the triple-Pomeranchukon coupling $g_{\mathrm{PPP}}(t, {q_1}^2, {q_2}^2)$ and its derivative $\frac{dg(t, q^2, q^2)}{d{q}^2}$ vanish when $t={q_1}^2={q_2}^2=0\mathrm{}$. A numerical estimate of the cut is given. We give the connection between the behavior of $g_{\mathrm{PPP}}$ and the validity of the Bronzan and Jones unitarity condition on the discontinuity of the cut at $t=0\mathrm{}$.

The red shift of the solar potassium absorption line at 7699 Å has been measured by means of an atomic-beam resonance-scattering technique. The shift at the center of the solar disk, corrected for Earth's motion, is ${\left(\Delta \lambda \right)}_{\exp }=(1.01\mathrm{}\pm 0.06){\left(\Delta \lambda \right)}_{\mathrm{theor}}$, where the theoretical value, based on the principle of equivalence, is 16.3 mÅ. Further data show negligible center-to-limb wavelength variation for this line.

We present the results of an exact calculation of the equations of motion (with gravitational radiation reaction terms) of a gravitating system subject to no external forces.

We prove, within the framework of analytic $S$-matrix theory and the physical mass spectrum, that the following scaling relations cannot be rigorously true for all $t$: (i) ${G_M}^V\mathrm{}\left(t\right)\mathrm{}\propto {G_E}^V\mathrm{}\left(t\right)\mathrm{}$, (ii) ${G_M}^V\mathrm{}\left(t\right)=R_1\mathrm{}\left(t\right)\mathrm{}{G_E}^V\mathrm{}\left(t\right)+R_2\mathrm{}\left(t\right)\mathrm{}$, where $R_{1,2}\mathrm{}\left(t\right)\mathrm{}$ are rational functions of $t$, (iii) $F_{\pi }\mathrm{}\left(t\right)\mathrm{}\propto {G_E}^V\mathrm{}\left(t\right)\mathrm{}$, and (iv) $F_{\pi }\mathrm{}\left(t\right)\mathrm{}\propto {G_M}^V\mathrm{}\left(t\right)\mathrm{}$.

Symmetries restrict isospin and SU(3) dependence of single-particle and multiparticle inclusive and semi-inclusive cross sections. Isospin relations test treatments of experimental data, including deuteron corrections, $\Lambda -{\Sigma }^0$ separations, and resonance-background separations. They also test the isospin structure of initial states in photoproduction, electroproduction, and neutrino-production processes; and they can reveal Coulomb effects in $\overline{p}d$ or $\overline{p}\alpha$ annihilation. Applied separately to beam and target fragments, they test diffractive excitation models.

The processes $\nu \left(\overline{\nu }\right)+\mathrm{target}\to \mathrm{hadron}+\mu \left(\overline{\mu }\right)+\mathrm{anything}$ are considered in the cases where the hadron selected has $I=\frac{1}{2} or 1$. Inequalities are given which follow from the conventional assignment of isospin to the weak current (for $\Delta S=0, 1$) and the charge-symmetry conditions for the $\Delta S=0\mathrm{}$ current. $\nu d$ and $\overline{\nu }d$ processes with $\Delta S=1\mathrm{}$ yield an equality if the hadron selected has $I=1\mathrm{}$. The hadronic analogs of these reactions are also discussed; bounds are given for ${\pi }^{-}+p\to \mathrm{hadron}+\mathrm{anything}$, which are stronger than those previously reported.

Our earlier experimental value for the $1s$ binding energy in ${}_{100}{}^{}{}_{}{}^{}\mathrm{Fm}$ (141.967±0.013 keV) agrees with a precision relativistic Hartree-Fock calculation using linear electrodynamics to 2±35 eV. This result is compared with a recent approximate calculation of the reduction (3.3 keV) in this binding energy when Born-Infeld nonlinear electrodynamics is used, and it indicates that such nonlinearities are limited to the order of 1% of Born-Infeld theory.

The comparison between the experimental binding energies for the $K$, $L$, and $M$ electrons for fermium and the results of our Dirac-Fock calculation, taking into account all tractable corrections, leads to agreement within about 20 eV. This shows that the present method of calculation is an adequate description of this problem and that nonlinear electrodynamical effects will not be present in nature or will be smaller than 1% compared to the values recently proposed. It is found that the energies of electronic transitions can now be used to estimate the nuclear radius.

We report the observation of an x-ray band which cannot be identified as a characteristic atomic x ray either of the target atoms or of the projectiles. The new x ray has been observed when 70-600-keV argon ions impinge on C, Al, Si, and Fe targets. We attribute this x ray to a radiative filling of a vacancy in the $2p\pi$ orbital of the Ar-Ar system during the collision.