High-resolution electron energy-loss measurements of ethylene on Ni(111) and cyclohexane on Ni(111) and Pt(111) show an extra CH stretching vibration—not found in free molecules or organometallic compounds—which is strongly broadened and shifted to lower frequencies relative to another, more typical CH stretching vibration. This softened and broadened CH frequency is attributed to a new electronic interaction with the surface which we relate to the mechanism of hydrocarbon dehydrogenation.

We report the pressure dependence of the three phase transitions in TTF-TCNQ as determined by resistivity measurements. There is only one transition above 15 kbar, and we find a 4-kbar regime centered at 20 kbar where the transition temperature peaks (the distortion temperature $T_d=71\mathrm{}$ K at 20 kbar), and the transition is first order. We suggest that there is a commensurate ×3 superlattice in this pressure regime resulting from an increase in charge transfer to $\frac{2}{3}$.

The Mössbauer effect of a dilute ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ impurity in Tc was measured for the first time. The isomer shift and the quadrupole splitting at room temperature are -0.02±0.01 and -0.13±0.02 mm/s, respectively. Small induced magnetic fields, -4.5±1 and -7.5±1 kOe, were found in external magnetic fields of 30 and 45 kOe at 4.2 K. This indicates that the magnetic character of Fe impurities in Tc lies in the intermediate region between magnetic and nonmagnetic. The induced field may be attributed to local spin fluctuation.

Approximate real-space (cell-type) renormalization-group methods are used to calculate the surface tension between coexisting phases in two- and three-dimensional Ising models. The results are physically reasonable and show the expected scaling properties near a critical point. However, there are some problems in reconciling the three-dimensional results with the existence of a roughening transition.

A mechanism for spontaneous symmetry breaking and related phenomena and the corresponding blocking of metastable states is discussed. It is based on the interaction of an object with a background of "probes" like photons or particles, etc., in its natural surrounding. Applications include quasilocalization of macroscopic bodies, spontaneous parity nonconservation of sugar crystals, localization of atoms in molecules (Born-Oppenheimer approximation), stability of metastable compounds, and perhaps also intrinsic symmetries of elementary particles.

We have studied the interactions of 400-GeV/c protons with beryllium nuclei and observed hadrons produced at large transverse momenta ($p_{\perp }$) back to back near 90° in the proton-nucleon center-of-momentum system. When both transverse momenta exceed about 2.6 GeV/c, we observe that the probability per single hadron of observing a second high-$p_{\perp }$ hadron on the opposite side approximately scales in the ratio of the two transverse momenta ($x_e$ scaling). Quantum-number correlations between the opposite-going high-$p_{\perp }$ hadrons are weak.

For both Abelian and non- Abelian gauge theories, we find gauge transformations which map fields in the $U$ gauge to other fields in the $U$ gauge. These transformations are not contained in the surviving gauge symmetry after spontaneous breaking (defined as the little group of the vacuum expectation value of the Higgs field). They have both discrete and continuous elements.

We study the effects on high-$p_T$ spectra of hadrons when partons are allowed to have transverse momentum (Fermi motion). We find the following: (i) The importance of Fermi motion depends crucially on the treatment of "soft" parton-parton collisions. (ii) We disagree with recent claims that values of $〈k_T〉\simeq 0.6$ GeV/c allow canonically scaling quark-quark scattering to describe the data. (iii) We show, furthermore, that even larger values of $〈k_T〉$, however implausible, cannot reconcile canonical scaling with the present data.

We show that the observation of the $A_1$ resonance in $\tau$ decay agrees with diffractive $A_1$ production and that it confirms our previous analysis of the diffractive data.

It is shown that if in a calculation of high-transverse-momentum meson production in hadron-hadron collisions one includes not only the scale-breaking effects that might be expected from asymptotically free theories but also the effects due to the transverse momentum of quarks in hadrons, then the results are not inconsistent with the single-particle cross-section data.

Measurements of statistical quantities other than the spectrum can distinguish between different $\frac{1}{f}$ noise mechanisms. One such quantity, the average behavior before and after a given fluctuation amplitude, is used to determine if the noise mechanism is linear. Measurements on different sources show that $\frac{1}{f}$ noise in some systems, such as carbon resistors and field-effect transistors, is due to a linear mechanism, while other systems, such as $p-n$ junction devices, require a nonlinear mechanism.

We compare high-transverse-momentum ($P_{\perp }$) inclusive ${\pi }^0$ production from ${\pi }^{-}$, $K^{-}$, $p$, and $\overline{p}$ beams, at 100 and 200 GeV/c, for center-of-mass (c.m.) angles ranging from 2° to 115° and $P_{\perp }<4.5\mathrm{}$ GeV/c. The ratio $\frac{\sigma (pp\to {\pi }^{0}X)}{\sigma (\pi p\to {\pi }^{0}X)}$ decreases with increasing $P_{\perp }$, and changes dramatically with c.m. angle. Also, the ratios $\frac{\sigma (K^{-}p\to {\pi }^{0}X)}{\sigma ({\pi }^{-}p\to {\pi }^{0}X)}$ and $\frac{\sigma (\overline{p}p\to {\pi }^{0}X)}{\sigma (pp\to {\pi }^{0}X)}$ are approximately constant. These measurements are consistent with a theoretical viewpoint in which constituents of the incident hadrons undergo a hard-scattering subprocess.

By considering a semisimple group [e.g., SU${\mathrm{}\left(4\right)\mathrm{}}^4$] subject to discrete symmetries which ensure one coupling constant in the unification limit, we show that the unification mass scale need be no higher than $1000m_W$. The possible emergence of a light octet of axial color gluons is noted.

Total-cross-section excitation functions for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ single and mutual inelastic scattering, and fusion, have been analyzed to yield partial widths of the $J^{\pi }=\left({10}^{+}\right), \left({12}^{+}\right), \mathrm{and} \left({14}^{+}\right)$ gross structure resonances. The results are shown to be consistent with the double-resonances picture in which the strongly collective $2_1^{+}$ inelastic excitations act as doorway states.

Pronounced periodic structure has been observed in the inelastic scattering of ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ for energies between 10 MeV and 23.6 MeV (center of mass). A similar effect is also seen in the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ reaction.

Strong-interaction shifts and widths for $2p$ levels in pionic atoms of Al, Si, S, Ca, Fe, Cu, and Zn have been measured with generally an order of magnitude better accuracy than before. Parameters of an effective pion-nucleus potential have been determined.

A recent Letter by Sparks and Sen challenges the viability of a recently proposed design for a commercial laser-fusion power plant. The basis for this challenge is the controversial theory of enhanced stimulated Raman scattering put forward by Sparks. This theory has been examined carefully. It is found to be in direct contradiction to both the classical and quantum theories of stimulated Raman scattering, and it is also in serious conflict with many experimental results.

Low-frequency ($\omega \ll {\omega }_{\mathrm{ci}}$) density fluctuations (which may be produced by the drift-wave instability of the cold-ion species) can stabilize the drift-cyclotron loss-cone (DCLC) mode by scattering electrons and thereby providing anomalous high-frequency resistivity to the DCLC mode.

An alternating electric field was applied to the (001) faces of a LiNb${\mathrm{O}}_3$ single crytal wafer, and the modulated fractions of the ($00h$)-diffracted intensities of x rays were measured by the synchronized detection. The displacements of Nb and Li ions relative to the oxygen framework were found to be 4.5×${10}^{-4\mathrm{}}$ and 9.8×${10}^{-4\mathrm{}}$ Å for the applied field of 51.5 kV/cm, respectively. The modulated fractions observed for the lower-indexed reflections give direct evidence for the redistribution of valence electrons which causes the electro-optic effect.

A high-resolution measurement of the optical birefringence has been made in 4-cyano-4′-octyloxybiphenyl to study in detail the orientational order parameter near the nematicsmectic-$A$ transition. There is no measureable discontinuity in the birefringence, but there is an abrupt change in its temperature coefficient at the transition. Contrary to the general impression obtained from published results, the behavior of the orientational order parameter does not follow the predictions of mean-field molecular and phenomenological theories, with or without fluctuations.