The narrow resonances at $M_{\psi }=3.105\mathrm{}$ GeV and $M_{{\psi }^{\prime }}=3.695\mathrm{}$ GeV are assigned, together with the familiar SU(3) nonet of vector mesons, as members of the 1 ⊕ 15 representation of SU(4). This leads to a solution consistent with the observed particle spectrum and accounts for the narrow widths of the $\psi$ and ${\psi }^{\prime }$. The masses of the charmed vector and pseudoscalar mesons are predicted.

Using a 16-GeV linearly polarized photon beam, we have measured asymmetries in the process $\gamma N\to K^{+}(\Lambda +\Sigma )$ from hydrogen and deuterium, for square of four-momentum transfer, $t$, between -0.01 and -0.8 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The data show that for $-t\gtrsim 0.1$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, the cross sections for $\gamma p\to K^{+}\Lambda$, $\gamma p\to K^{+}{\Sigma }^0$, and $\gamma n\to K^{+}{\Sigma }^{-}$ are strongly dominated by natural-parity exchange, as is the case in single-pion photoproduction.

The spin polarization of photoelectrons emitted by thallium atoms exposed to circularly polarized light has been measured between 1400 and 1700 Å. The polarization curve shows a pronounced structure which is determined by the autoionization resonances. The results are explained on the basis of Fano's resonance theory.

The polarization of photons from the transition $3{}_{}{}^3{}_{}{}^{}P\to 2{}_{}{}^3{}_{}{}^{}S$ and the angular distribution of radiation from the decay $2{}_{}{}^1{}_{}{}^{}P\to 1{}_{}{}^1{}_{}{}^{}S$ emitted in ${\mathrm{He}}^{+}$ +He collisions at an incident energy of 150 eV and an ion scattering angle of 13.5° were measured by detecting the scattered ions and photons in delayed coincidence. From these measurements we conclude that the $3{}_{}{}^3{}_{}{}^{}P$ excitation takes place through a $\Sigma -\Sigma$ radial coupling, and the $2{}_{}{}^1{}_{}{}^{}P$ excitation predominantly through a $\Sigma -\Pi$ rotational coupling, probably at large internuclear separation.

We have measured the electron-loss cross section for collisions between protons and highly excited hydrogen atoms having principal quantum numbers in the nominal $n$ band $44\lesssim n\lesssim 50$. The c.m. collision energy range was $0.4 \mathrm{eV}<~W<~61 \mathrm{eV}$. Theoretical ionization-cross-section results are compared with the data and are then used to unfold from the data the approximate electron-transfer cross section. Classical scaling calculations are found to be in reasonable agreement with the unfolded data while quantal predictions are not.

Quasielastic neutron scattering experiments on terephthal-bis-butylaniline (TBBA) show that the phenyl rings do not have a strongly preferred orientation in the smectic-$H$ (tilted $B$) phase. This suggests that the Meyer-McMillan model is not quite adequate for this particular system.

Precision measurements of the viscosity ($\eta$) of liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at the saturated vapor pressure over the range $2.0\times {10}^{-6\mathrm{}}\lesssim \left|\epsilon \right|\lesssim 5.5\times {10}^{-3\mathrm{}}$ ($\epsilon =\frac{T}{T_{\lambda }}-1\mathrm{}$) have revealed a singularity of the form $\frac{\eta }{{\eta }_{\lambda }}-1=-A^{\prime }{(-\epsilon )}^{0.65\pm 0.03}$ below $T_{\lambda }$ and $\frac{\eta }{{\eta }_{\lambda }}-1=A{\epsilon }^{0.80\pm 0.05}$ above $T_{\lambda }$.

The thermal boundary resistance between powdered cerium magnesium nitrate and solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ was measured in the temperature range between 45 and 250 mK. The phonon bottleneck as well as the phonon-dependent boundary resistance was observed. At low temperatures we observed a magnetic Kapitza resistance in parallel with that due to the phonons. The magnetic Kapitza resistance is proportional to $T^2$ in agreement with theoretical predictions.

Low-impedance diodes with hollow tapered cathodes produce strong self-pinching in intense relativistic electron beams. Early in the pulse a thin hollow beam is formed, based on evidence of electrons striking the anode. This hollow beam collapses, accelerating toward the diode axis with velocities (1 to 5 mm/nsec) which depend locally on the anode material. An efficient and stable pinch, less than 3 mm in diameter, is formed at the anode. In the center 0.1 ${\mathrm{cm}}^2$, the power rises to ${10}^{11}$ W in less than 3 nsec. About 50% of the total diode energy (∼ 9 kJ) is dissipated within the pinch region.

The propagation of current-driven ion-acoustic waves in a positive column is studied by measuring the cross-power spectral density up to 30 MHz. Dispersion characteristics are verified in the weakly turbulent state, and the measurements of instability correlation times and lengths are illustrated for higher levels of turbulence, where the dispersion relation no longer applies.

Electronic transitions between the ${}_{}{}^7{}_{}{}^{}F_J^{}{}_{}{}^{}$ multiplet levels of ${\mathrm{Sm}}^{2+}$ have been observed optically in SmS, SmSe, SmTe, and ${\mathrm{Sm}}_{1-x}{\mathrm{Y}}_x\mathrm{S}$. In SmS, SmSe, and SmTe, the strong temperature dependence of the singlet-triplet energy is well described by the random-phase-approximation results of Wang and Cooper, allowing us to determine both the exchange and the spin-orbit interaction. However, no temperature dependence of the singlet-triplet energy is observed in metallic ${\mathrm{Sm}}_{1-x}{\mathrm{Y}}_x\mathrm{S}$.

Inelastic neutron scattering measurements of the ${\mathrm{Sm}}^{2+}$, ${}_{}{}^7{}_{}{}^{}F_0^{}{}_{}{}^{}\to {}_{}{}^7{}_{}{}^{}F_1^{}{}_{}{}^{}$ singlet-triplet exciton dispersion in semiconducting SmS at 77, 197, and 273°K are reported. The results are in good agreement with current theory predicting the temperature dependence of the singlet-triplet excitations. The ${}_{}{}^7{}_{}{}^{}F_0^{}{}_{}{}^{}-{}_{}{}^7{}_{}{}^{}F_1^{}{}_{}{}^{}$ separation is found to be (420 ±2)°K, in agreement with the free-ion value of 422°K, while the exchange interactions are characteristic of a magnetic semiconductor. The implications for the Sm-ion eigenstate are discussed.

Measurements of the specific heat of ${\mathrm{K}}_2$Pt${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4$${\mathrm{Br}}_{0.3}$·3(${\mathrm{H}}_2$O) between 0.059 and 40 K reveal three unexpected features: (1) a contribution linear in temperature above ∼0.15 K, (2) a sharp decrease in this linear contribution below ∼0.15 K, and (3) a marked dependence upon the state of hydration of the sample above 6 K.

We present the $N_{4,5}$ appearance-potential spectrum of La. Structure exists at energies lower than the threshold energy for transitions terminating at the Fermi level. Several similarities between optical absorption spectra and our results are discussed. These results contradict the simple model usually used to interpret appearance-potential spectra and emphasize the need for a new theory.

Recent measurements of apparent absorption saturation and ultrafast relaxation in Ge have been reinterpreted as a parametric coupling between optical beams due to an index grating produced by a high-density electron-hole plasma. A sharp spike in probe-beam transmission of width 2 psec observed near zero time delay between a strong pumping and a weak probing beam has been shown to be the autocorrelation of the optical electric fields. In addition, evidence of a true saturation effect with a much longer recovery time is observed.

It is pointed out that certain phase transitions which involve a doubling of the unit cell are described by $n$-component vector models with $n>~4$. In particular, it is noted that the structural transition in Nb${\mathrm{O}}_2$ is described by an $n=4\mathrm{}$ component model with some tetragonal anisotropy. The critical behavior of this model is studied to order ${\epsilon }^2$, by the exact renormalization group in $d=4-\epsilon$ dimensions. It is found that the critical behavior is determined by a new, tetragonal, fixed point.

We detected and identified He ions, predominantly $\alpha$ particles, in the reaction ${\pi }^{-}+{}_{}{}^{27}{}_{}{}^{}\mathrm{Al}\to \mathrm{He}+X$ at $E_{\pi }=70\mathrm{}$ MeV. The differential cross section at 90° is 6±2 mb/sr in the energy range $E_{\mathrm{He}}=5.5-30\mathrm{}$ MeV. The He yield decreases from 7 to 25 MeV, where it approaches zero.

Measurements and various $s$-wave model calculations of $p+d$ breakup cross sections were made along constant-relative-energy loci as suggested by Jain, Rogers, and Saylor. The measurements utilized special gas scattering apparatus to accurately measure cross sections in the vicinity of destructive interference minima. The data agreed with the most realistic of the models used except at the position of the interference minimum where a discrepancy of a factor of 3 was found.

The quadrupole and hexadecapole moments of ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ were derived from the hfs of the $3d$ muonic states. The resulting values are $Q_0=7.44\mathrm{}\pm 0.07$ b and ${\Pi }_0=0.52\mathrm{}\pm 0.10$ ${\mathrm{b}}^2$. The parameters of the nuclear charge distribution were determined. An indication for an angular variation of the skin thickness was found.

H, He, and heavy ions of energies ≥ 0.12 MeV/charge were detected in the magnetotail and in the magnetosheath. It was found that their relative abundances were ∼9:1:4×${10}^{-2\mathrm{}}$, their differential energy spectra were $\sim \frac{1}{E^4}$, and their atomic electrons were almost completely stripped. These results led us to suggest that they were the low-energy "quiet-time" cosmic rays accelerated within the magnetotail and the magnetosheath to the observed energies.