The surface exponents associated with critical phenomena in semi-infinite systems are derived exactly in terms of bulk exponents. Results are ${\gamma }_{1,1}=\nu -1\mathrm{}$, ${\gamma }_1=\nu +\frac{(\gamma -1)}{2}$, ${\beta }_1=\frac{(3-\alpha )}{2}-\nu$, ${\Delta }_1=\frac{(1-\alpha )}{2}$, ${\eta }_{\parallel }=\frac{1}{\nu }$, and ${\eta }_{\perp }=1-\frac{(\gamma -1)}{2\nu }$, where $\nu$, $\gamma$, $\alpha$, etc., are the standard bulk exponents. The bulk-surface crossover exponent is ${\varphi }_s=1-\nu$. For $\nu >1\mathrm{}$ no surface phase can exist.

Based on a scan for converted $e^{+}{e}^{-}$ pairs in a large neutrino exposure of the Argonne National Laboratory twelve-foot bubble chamber, we report an upper limit of $m_{{\nu }_{\mu }}{\Gamma }_{{\nu }_{\mu }}<4.6\mathrm{}\times {10}^{-4\mathrm{}}$ MeV/sec for the process ${\nu }_{\mu }\to \gamma +X$, where $X$ satisfies appropriate conservation laws.

We use new measurements of the inclusive electroproduction reactions $\mathrm{eN}\to e^{\prime }{\pi }^{\pm }X$ and $\mathrm{eN}\to e^{\prime }\mathrm{pX}$ with $\epsilon$ values in the range $0.35<\mathrm{}\epsilon <0.45\mathrm{}$ together with earlier measurements with $0.85<\mathrm{}\epsilon <0.95\mathrm{}$ to determine the contributions to the cross section due to transversely and longitudinally polarized photons in the range $1.2 \mathrm{Ge}{\mathrm{V}}^2<Q^2<3.3\mathrm{} \mathrm{Ge}{\mathrm{V}}^2$. The longitudinal component is small and consistent with that observed in the total virtual-photoproduction cross section.

For the reaction ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ + ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ at a laboratory bombarding energy per nucleon of 250 MeV we calculate the cross section $\frac{d^2\sigma }{\mathrm{dEd}\Omega }$ for outgoing protons using four different approaches. These are relativistic fluid dynamics, classical many-body calculations with a hard-sphere nucleon-nucleon potential, and two versions of relativistic intranuclear-cascade calculations. These calculations reproduce some features of the experimental data, but some major discrepancies remain.

We have measured the differential cross section for 50-MeV ${\pi }^{+}$ scattering to the ground state, $2^{+}$ (4.44 MeV) and $3^{-}$(9.64 MeV) of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. Both elastic and $2^{+}$ data show a minimum at ∼65°. Distorted-wave Born-approximation calculations yield excellent agreement with the inelastic data when the entrance and exit channels are distorted using a phenomenological optical potential which describes the elastic data.

Some features have been observed for the first time around 69 eV in the electron-impact differential excitation cross section of the bound state $2{}_{}{}^3{}_{}{}^{}S$ of helium, measured in the forward direction. The main feature, which involves a variation of about 2.8×${10}^{-21\mathrm{}}$ ${\mathrm{cm}}^2$ ${\mathrm{sr}}^{-1\mathrm{}}$ in the cross section, may be assigned to the negative-ion state $3s^{2}3p\left({}_{}{}^2{}_{}{}^{}P\right)$ thus lying at about 68.98±0.07 eV; a second feature is observed at about 69.67±0.08 eV. The detection of these resonances has a special interest because the decay of these ${\mathrm{He}}^{-}$ states involves the three electrons concerned in the collision process.

A tractable form of the fixed-scatterer approximation retaining up to double-scattering terms has been proposed. This formalism can be employed to investigate the elastic as well as inelastic processes at intermediate and high energies. The results for the differential cross section for the elastic scattering and for excitation of the $n=2\mathrm{}$ states of H atom in $e^{-}$-H scattering are found to be very encouraging, computational labor involved for $s-s$ transitions being comparable to that of the first Born calculations.

In a technique using a continuum generated by focusing a laser beam on a target of high atomic number, the spatially resolved absorption spectrum of ${\mathrm{Li}}^{+}$ formed in a second laser-produced plasma was studied from 200 to 50 Å. The doubly excited resonances, $1s^2{}_1{}^{}{}_{}{}^{}S-2\mathrm{snp}{}_{}{}^1{}_{}{}^{}P$, as well as the principal series and its adjoining photoionization continuum were observed. The Fano parameters, $q$ and $\Gamma$, of the $2s2p{}_{}{}^1{}_{}{}^{}P$ were derived from the absorption profile. Comparison is made with theory.

Enhanced population of the $n=4\mathrm{}$ excited state is measured in both ${\mathrm{C}}^{4+}$ and ${\mathrm{C}}^{5+}$ ions in agreement with a theory for formation by resonance charge transfer between carbon ions and atoms. A background gas modifies and mixes the interacting particles originating from a carbon surface vaporized by a focused laser beam. Population inversions capable of producing quasi-cw amplification in the extreme ultraviolet region are measured.

For configuration states such as $2p^{5}3p^5{}_{}{}^1{}_{}{}^{}S$, ${}_{}{}^3{}_{}{}^{}P$, ${}_{}{}^1{}_{}{}^{}D$ the Hartree-Fock method produces total wave functions with an incorrect form as the atomic number $Z\to \infty$. It is shown how a correct form can be obtained, with similar accuracy as the Hartree-Fock wave function, for a statistically weighted average of $2p^{5}3p^5{}_{}{}^3{}_{}{}^{}S$, ${}_{}{}^1{}_{}{}^{}P$, ${}_{}{}^3{}_{}{}^{}D$.

We report the observation of optical amplification in a two-level atomic system driven by a strong, resonant field. By exciting an atomic beam of two-level sodium atoms simultaneously with a strong, fixed-frequency driving field and a weak, tunable, probe field, we have measured the absorption (amplification) line-shape function for several values of driving field strength. In addition, we have verified theoretical predictions that higher amplification is obtained when the strong field is detuned from exact resonance.

The divergent intensity of the central peak observed in Brillouin scattering spectra in potassium dihydrogen phosphate has been studied in the paraelectric phase and found to be $\mathrm{VH}$ polarized and to show "speckle" interference fringes. This implies that the scattering centers have time-independent amplitudes and positions. Photographs of the scattering column at different temperatures near the phase transition show that the scattering-center configuration is temperature independent.

The simultaneous high-energy-resolution and high-angular-resolution (15 meV, 0.8°) measurements of the (00) beam diffracted from W(001) near 45° incident angles are reported. Apart from the well-known surface-state resonance previously identified, new features located in the close vicinity of the ($\overline{1}0$) emergence energy are detected. They may remain undetected if one of the two high-resolution requirements is not fulfilled. The threshold effects are correlated with the ($\overline{1}0$) beam emergence by angular distribution and $I-V$ measurements, and possible interpretations are discussed.

A band of unbound surface states (resonances), located in an energy region above the vacuum threshold corresponding to an energy band gap in the electron states of the bulk crystal, has been observed by angle-resolved secondary-electron-emission spectroscopy. The experimental dispersion behavior is in agreement with the two-dimensional band structure of a clean (001)W surface recently proposed by Smith and Mittheiss.

Al-${\mathrm{Al}}_2$${\mathrm{O}}_3$-Al tunnel junctions were used to measure large increases in the energy gap of superconducting aluminum films in the presence of 10-GHz microwave radiation. When the microwave power was increased at constant temperature, enchancement occurred only for temperatures at which twice the equilibrium energy gap exceeded the photon energy. When the temperature was increased at constant microwave power, enhancement was observed at higher temperatures.

By monitoring the change in the conduction-band optical density of states (CBODOS) and the bonding shifts of the core levels, we observe an electronic transfer from Bi to oxygen atoms during Bi oxidation. Similar analysis of the CBODOS of other Bi and Pb chacogenides indicates a partial ionicity in these compounds which correlates with electronegativities and the chemical shifts of the core levels.

Raman-scattering selection rules for surface polaritons have been studied by experiments using a thin (≈ 20 μm) single-crystal slab of GaP of known orientation. The dispersion of the observed mode has been determined by varying the scattering angle, and comparison is made with the theoretically predicted dispersion of surface polaritons at the surface of a semi-infinite GaP crystal. The observed selection rules are consistent with the results of an analysis using the bulk Raman tensors.

A counter-spark-chamber experiment has been done in the alternating-gradient synchrotron's 23-GeV/c charged hyperon beam to study $Y^{*}$ production in reactions of ${\Sigma }^{-}$ on ${\mathrm{H}}_2$, Al, Cu, W, and Pb in which the $Y^{*}$ decays into the ${\Lambda }^0-{\pi }^{-}$ final state. We observe the ${\Sigma }^{*}\mathrm{}\left(1385\right)\mathrm{}$ and place upper limits on possible diffractively produced $Y^{*}$ resonances and on the Coulomb production of the ${\Sigma }^{{*}^{-}}\mathrm{}\left(1385\right)\mathrm{}$.

We report the results of a precise measurement of the $K^{-}p\to {\overline{K}}^{\circ }n$ cross section between 515 and 1065 MeV/c in steps of 10 MeV/c. The statistical errors are less than 1%, a major improvement in accuracy over previous work. No evidence is found for the new $I=1\mathrm{}$ $\overline{K}N$ resonances at 546 and 602 MeV/c reported recently by Carroll et al.

Utilizing the $K^{-}p$ charge-exchange results from the previous Letter, we report an energy-dependent partial-wave analysis of all available $\overline{K}N$ data from 365 to 1320 MeV/c. The effects observed at $\Lambda \eta$ and ${\Sigma }^0\eta$ thresholds are well described by cusps. New values of masses and widths are found for the $P_{01}$ and $P_{11}$ resonances. No new narrow resonances are required.