Magnetic fields were found to decrease rhodamine-$B$—sensitized delayed fluorescence in anthracene by up to 60% at 10 mTorr. An inverse but smaller effect was found on sensitized photoconductivity. The observations are explained in terms of a magnetic-field-dependent recombination of surface electrons and injected holes, with the field scale being fixed by hyperfine interactions.

The intrinsic four-body relaxation mechanism can successfully explain the seemingly mysterious wall-mobility data recently reported by Rossol in YFe${\mathrm{O}}_3$. The monotonic decreasing temperature dependence of the wall mobility measured in YFe${\mathrm{O}}_3$ is a direct consequence of (1) the antisymmetric exchange interaction confining the magnetization to the $a-c$ plane, (2) the domain wall being of the Néel type, and (3) the sample shape factor. The calculated results are in excellent agreement with Rossol's data.

We have measured the masses of ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ti}$ and of the previously unknown nuclei ${}_{}{}^{47}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{51}{}_{}{}^{}\mathrm{Fe}$, and ${}_{}{}^{55}{}_{}{}^{}\mathrm{Ni}$. These proton-rich members of $1f_{\frac{7}{2}}$-shell mirror pairs are important for extensions of nuclear mass relationships to the $Z>N$ region.

A method for solving Faddeev equations in configuration space is used to study the state of three nucleons bound in a Reid potential. Including $D$ states for the spectator particle gives a binding energy of 6.6 MeV, probabilities $P_{S^{\prime }}=1.9\%$, $P_D=7.9\%$, and a charge radius $r_c\left({}_{}{}^3{}_{}{}^{}\mathrm{He}\right)=1.97\mathrm{}$ fm; the dip in the charge form factor is found at $q^2=14.5\mathrm{}$ ${\mathrm{fm}}^{-2\mathrm{}}$.

We have studied a system consisting of a particle coupled to a rotating core. Although a complete decoupling of particle and core occurs only at very small deformations (coupling strengths), a "favored" high-spin band of levels tends to be decoupled over a much larger region of deformation. This can be understood as a simple Coriolis effect, and seems to be borne out remarkably well in some odd-$A$ La isotopes.

Data were obtained for ($p,t$) reactions on ${\mathrm{Cd}}^{112,114,116}$, with $E_p=27.9\mathrm{}$ MeV. The angular distributions for $J^{\pi }=0^{+} \mathrm{and} 2^{+}$ two-phonon states differ markedly in phase from zero-and one-phonon transitions. The ratios of cross sections to the $2^{+}$ states are systematically an order of magnitude larger than expected from $B\left(E2\mathrm{}\right)\mathrm{}$ ratios. Two-step mechanisms are suggested.

We have measured the charge composition of cosmic-ray nuclei from Li to Fe with energies up to about 100 GeV/nucleon. A balloon-borne counter telescope with gas Cherenkov counters for energy determination was used for this experiment. Our first results show that, in contrast to low-energy observations, the relative abundances change as a function of energy. We find that the ratio of the galactic secondary nuclei to primary-source nuclei decreases at energies above about 30 GeV/nucleon.

We present a compilation of existing data on inclusive reactions which provide evidence for the factorization hypothesis in the "central" region of pion production but only at infinite beam momentum. The approach to limiting behavior in the central region is consistent with that expected on the basis of the Mueller-Regge formalism.

We present a simple means of separating a partial-wave amplitude into a resonant term plus an inelastic background. The separation is exact if only one inelastic channel is present, but it should be a good approximation in the presence of more than one inelastic channel. Inequalities are obtained relating the elastic and inelastic widths to the background inelasticity. Comments are made regarding the application of the formalism.

We have measured cross sections for chemi-ionization in thermal energy collisions of $\mathrm{He}\left(2^{1}S\right)$ and $\mathrm{He}\left(2^{3}S\right)$ metastable atoms with argon using both crossed-beams and gas-cell techniques. The results indicate that several earlier measurements of these cross sections were in error.

We investigated the line shape of the Lyman-$\alpha$ transition of a hydrogen atom simultaneously subjected to a static and a perpendicular high-frequency electric field. It was found that resonance effects occur, producing a profile substantially different from the Stark spectrum of the fields acting independently. This result shows that the interpretation of turbulent hydrogen plasma spectra by the Blokhintsev (dynamic field only) theory is not generally valid.

We have observed a broad $P$-wave resonance at about 50 eV primary energy in the angular distribution of electrons scattered after excitation of the $2^{3}S$ state of helium. The resonance has a width of about 15 eV and affects the differential excitation cross section by more than 3 orders of magnitude. It is suggested that this resonance is associated with the temporary formation of triply excited states of the negative helium ion.

The energy shifts of Fe, Co, Zr, and Sn $K$ x rays produced by 5-MeV/amu He, C, O, Ne and 10 MeV/amu C ions depend nearly linearly on the stopping power for the bombarding ion. The shifts and the $\frac{K\beta }{K\alpha }$ ratios show a projectile energy dependence similar to that predicted for the $L$-ionization cross section. This suggests that these phenomena can be explained by existing Coulomb excitation theories.

Absolute differential and total cross sections for the scattering of CsF by 0.6- to 6.5- eV electrons have been measured using the molecular-beam recoil technique. The first-Born-approximation differential cross section is used as the theoretical model to fit the data. The experimental differential cross sections rise more sharply near 0° than predicted. Total cross sections derived from our measurements are a factor of 1.5 to 4 smaller than the first-approximation results.

A pressure shift of the magnetic resonance line of the $3s_2$ level of neon in a He-Ne laser operating at 0.633-μm $\pi$ transitions was observed by varying the partial pressure of helium. The shift in the resonant angular frequency was (2.8 ± 0.5) × ${10}^7$ ${\sec }^{-1\mathrm{}}$ ${\mathrm{Torr}}^{-1\mathrm{}}$, and the ratio $a$ of the shift to the pressure broadening (half width at half-maximum) was 0.78 ± 0.14.

The intermolecular and intramolecular spin-lattice relaxation times have been determined by isotopic dilution for the nematic and isotropic phases of $p$-asozyanisole. Derived correlation times for rotational and translational motions suggest that these processes are strongly coupled in the nematic phase. Comparison of rotational correlation times with results from dielectric studies indicates that rotational reorientation occurs by large jumps (greater than 60°) in the nematic phase.

A nonlinear theory is presented for the saturation of the current-driven ion-acoustic instability. The saturation mechanism is the modification of ion orbits by finite-amplitude waves, leading to ion trapping. The results are quantitatively compared with recent computer simulations of Biskamp and Chodura, and experiments of Hamberger and Jancarik.

A universality hypothesis relates the amplitude of the singular parts of the coherence length and the specific heat (or surface tension). For the spin-½ Ising model it is exact in two dimensions and numerically accurate to within 1% in three. It is consistent with measurements on the "Ising-like" systems C${\mathrm{O}}_2$, Xe, and $\beta$-brass and the "Heisenberg-like" systems RbMn${\mathrm{F}}_3$ and EuS to within experimental uncertainties (∼ 20%). It provides a sensitive and experimentally convenient indicator of symmetry ("universality") class.

The tricritical behavior of a classical three-well-potential model for two-component systems (such as ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures) is discussed by using renormalization-group techniques. The tricritical exponents and scaling fields are calculated for three dimensions.

The phonon anomalies observed in superconducting TaC have been explained recently by Weber, Bilz, and Schröder with their extended shell model. Their model also predicts an anomaly in the transverse acoustic mode in the [110] direction with $\mathrm{xy}$ polarization—a branch which was not measured in the initial neutron investigation. The purpose of this Letter is to report the experimental confirmation of the Weber-Bilz-Schröder prediction, which gives added credence to their model, and to comment on the possible significance of these results.