A microscopic theory is presented for the photoacoustic effect induced in solids by x-ray absorption. The photoacoustic effect results from the thermalization of the excited Auger electrons and photoelectrons. We explain the dependence of the photoacoustic signal $S$ on photon energy and the proportionality to the x-ray absorption coefficient in agreement with recent experiments on Cu. Results are presented for the dependence of $S$ on photon energy, sample thickness, and the electronic structure of the absorbing solid.

For the two-impurity Kondo system, the low-temperature properties—impurity spin-spin correlation function, susceptibilities, specific heat, and Wilson ratio—are strongly nonuniversal functions of the ratio $\frac{I_0}{T_{\mathrm{K}}}$ of the Ruderman-Kittel-Kasuya-Yosida coupling to the single-impurity Kondo temperature. In particular, there is a new unstable fixed point for an antiferromagnetic coupling with $\frac{I_0}{T_{\mathrm{K}}}\simeq -2.2\mathrm{}$. The calculations utilize a newly found symmetry of Kondo Hamiltonians, axial charge.

In a type-II GaAs-AlAs multiple quantum well three optically detected magnetic resonance lines and two level anticrossings were observed. Two of the resonance lines and the two level anticrossings are in agreement with the electronic level scheme of the heavy-hole exciton. The third resonance line is in accordance with a magnetic spin resonance of an unbound electron. These optically detected magnetic resonance measurements open up the possibility to obtain detailed information about the excitons in and the band structure of type-II quantum wells.

We present a solution of the mode-coupling equations for the dynamics of critical fluctuations which incorporates the crossover from the singular behavior of the transport properties of fluids asymptotically close to the critical point to the regular behavior of these properties far away from the critical point. Good agreement is obtained with experimental thermal diffusivity, thermal conductivity, and viscosity data for carbon dioxide at all temperatures and pressures where critical effects in these transport properties are observed.

We show that an evolving geometric phase induces a frequency shift. We report an optical experiment where we employ this effect to offset the frequency of a laser beam.

A neutrino magnetic moment greater than $10_{}^{-12\mathrm{}}{}_{\mathrm{\mu }\mathrm{B}}{}^{}$, the Bohr magneton, would have important implications for gravitational-collapse supernovae. Also, it has been suggested that $\frac{\mu }{{\mu }_B}\sim {10}^{-10\mathrm{}}$ might solve the solar neutrino problem. However, we show that the neutrino observations of SN1987A and general optical observations of supernovae set a firm upper limit of $\frac{\mu }{{\mu }_B}<5\mathrm{}\times {10}^{-13\mathrm{}}$. This limit is about 100 times better than the best experimental determination and previous astrophysical limits, and 10-20 times better than a previous limit based on big-bang nucleosynthesis.

We consider the possible emission of right-handed neutrinos $v_R$ from SN1987A by neutrinomagnetic-moment interactions. By imposing a bound on the $v_R$ luminosity, we get a limit on the neutrino magnetic moment, ${\mu }_v<(0.2-0.8)\mathrm{}\times {10}^{-11\mathrm{}}{\mu }_B$, depending on the core temperature. It appears that consideration of the number of high-energy ($E\simeq 100-200$ MeV) neutrino events that should have been observed in the underground detectors, after $v_R\to v_L$ rotation in the galactic magnetic field, may lead to a stronger bound, ${\mu }_v<({10}^{-13\mathrm{}}-{10}^{-12\mathrm{}}){\mu }_B$, under specific assumptions.

Spectral fluctuation properties in the optical-fluorescence excitation spectrum of N${\mathrm{O}}_2$ are investigated. For this purpose new high-resolution measurements have been performed. We analyze the distribution of intensities and of level spacings and the spectral rigidity. Together with the consideration of effects of missing and spurious lines, the presence of random-matrix fluctuations is demonstrated unambiguously.

Within the nonperturbative unification framework pioneered by Maiani, Parisi, and Petronzio, it is shown how the mass of the right-handed $W$ boson can be determined just by knowledge of the values of ${sin}^2{\theta }_W$ and ${\alpha }_3\left(\equiv \frac{g_3^2}{4\pi }\right)$ at the Fermi scale ${\Lambda }_F\approx 250$ GeV. It is found that $M_{W_R}$ can be as low as 8 TeV and, as a consequence, it may be possible to detect $W_R$ at the proposed Superconducting Super Collider. In the model considered here, light Majorana neutrino masses are found to be small (< 65 eV).

By use of unitarity of the Kobayashi-Maskawa matrix, the rephasing-invariant measure ${\delta }_{\mathrm{KM}}$ of $\mathrm{CP}$ nonconservation is evaluated in terms of the moduli squared of four matrix elements, which are taken as the four independent parameters. The striking feature of such a formulation is that the positivity of ${\delta }_{\mathrm{KM}}^2$ gives both upper and lower bounds on the matrix elements $\left|V_{\mathrm{cd}}\right|$, $\left|V_{\mathrm{cs}}\right|$, $\left|V_{\mathrm{td}}\right|$, and $\left|V_{\mathrm{ts}}\right|$.

We study a ring-diagram approach for nuclear matter where the particle-particle and hole-hole ring diagrams are calculated to all orders via a random-phase-approximation equation. This equation is found to have complex eigenvalues within a small temperature-density region, and our results suggest that this occurrence of complex eigenvalues may be a useful signal for nuclear-matter phase transitions. With a slightly modified Gogny interaction, our ring-diagram nuclear-matter calculations give ${\rho }_0=0.17\mathrm{}{\mathrm{fm}}^{-3\mathrm{}}$, $\frac{E_0}{A}=-15.9\mathrm{}$ MeV, $K=127\mathrm{}$ MeV, and the liquid-gas critical temperature $T_c=7.6\mathrm{}$ MeV.

Several rotational-band structures have recently been observed in mass $A\simeq 130$ nuclei, built on multiquasiparticle states of enhanced quadrupole deformatin, the so-called superdeformed states $\beta \simeq 0.4$. In ${}_{}{}^{137}{}_{}{}^{}\mathrm{Sm}$, a decoupled band built on the ${\mathrm{vi}}_{\frac{13}{2}}\mathrm{}\left[660\right]\mathrm{}{\frac{1}{2}}^{+}$ single-quasineutron orbital, intruding from two oscillator shells above with a predicted $\beta \simeq 0.35$, was observed to low spin and excitation energy. The role of this $\beta$-driving ${\mathrm{vi}}_{\frac{13}{2}}$ orbital, which showed a 50% enhanced moment of inertia, is discussed in terms of the superdeformation in this mass region.

States in ${}_{}{}^{154}{}_{}{}^{}\mathrm{Dy}$ have been located up to $I^{\pi }={48}^{+}$ and their lifetimes measured. Marked structural changes occur along the yrast line with a transition from prolate to oblate shape, followed by an unexpected return to moderate collectivity at the highest spins. Structural changes with increasing energy above the yrast line are also observed.

Correlation measurements of mixed signal and idler photons produced in the process of parametric down-conversion have been performed as a function of two linear polarizer settings. It is found that the Bell inequality for two separated particles is violated by about 6 standard deviations, and that classical probability for light waves is violated substantially also.

When signal and idler photons produced in the process of parametric down-conversion are mixed together, and directed to two photodetectors that respond to nonoverlapping optical frequencies centered at ${\omega }_1$ and ${\omega }_2$, it is found that the joint probability of two-photon detection exhibits a modulation of the form $cos({\omega }_1-{\omega }_2)\tau$, where $c\tau$ is the path difference. The experimental results are well described by a simple quantum-mechanical analysis.

The $6^1{S}_0-6^3{P}_1$ electron-impact excitation of mercury has been studied by a combination of the techniques of electron-photon coincidence and polarized-electron scattering. Spin-up-down asymmetries were measured at collision energies of 8 and 15 eV and scattering angles ranging from 5° to 120°. Linear light polarization filters allowed the separate observation of the $M_J=0\mathrm{}$ and $M_J=\pm 1$ sublevel excitations and the determination of the linear light-polarization component $\zeta$ 3. The experimental data yield detailed information about the influence of different spin-dependent interactions on electron-impact excitation.

We suggest the use of mixtures of light and heavy elements as targets for laser-driven femtosecond-time-scale x-ray line radiators. It is shown that the essential cooling of a heavy metal together with the loss-modified thermal conductivity allows an x-ray pulse to replicate a laser pulse on a femtosecond time scale, and to achieve such an x-ray pulse, the density of heavy metal must be reduced to a level commensurate with the absorbed laser energy. Results of numerical modeling for the generation of 3.6-Å x rays in a mixture of Li and Sn are given.

Measurements of the single-shot power spectrum of stimulated Raman scattering from an ${\mathrm{H}}_2$ Raman generator at 10 and 32 atm using a Fabry-Perot interferometer are presented. The results show that the single-shot linewidth can be much narrower than the ensemble average predicted by quantum mechanics. However, when the spectra of numerous shots are averaged together the resulting linewidth is in close agreement with the predicted result. In addition, the power spectrum exhibits large shot-to-shot fluctuations within the gain-narrowed profile which may be related to observed soliton decay in stimulated Raman scattering.

It is shown that the negative diffusion coefficients exhibited by the current approaches to the Fokker-Planck equation for non-Markovian and bistable processes result from assuming the diffusion process to be stationary. The rejection of this assumption leads to predictions on the escape over a barrier agreeing with the physical arguments pertaining to the extremely colored-noise regime.

We report narrow dielectronic-capture resonances decaying by double autoionization, observed for the first time in electron-impact ionization of ions. We also observe corresponding peaks in double and triple ionization leading us to postulate new processes where dielectronic capture is followed by triple or quadruple autoionization, respectively.