We have calculated the two-neutrino and no-neutrino, lepton-number-nonconserving double beta decay rates for ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{82}{}_{}{}^{}\mathrm{Se}$. Our result for the two-neutrino decay of ${}_{}{}^{82}{}_{}{}^{}\mathrm{Se}$ is in agreement with a recent cloud-chamber measurement and thus in disagreement with the geochemical determination. We find that a constraint on the Majorana mass of the electron neutrino of ${〈m〉}_{\nu }\gtrsim 15$ eV follows from the comparison of our calculations and the experimental limits on the neutrinoless decays of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{82}{}_{}{}^{}\mathrm{Se}$.

We show that the relativistic many-body theory that has recently been used to explain the saturation properties of nuclear matter also explains the remarkable density dependence (found in phenomenological studies) of the Landau-Migdal parameter, $F_0$. This result provides further evidence that the nucleus is a relativistic system.

Mass spectra of Pb, NaI, and Xe microclusters show that below a critical number of atoms per cluster, $n^{**}$, doubly charged particles are not stable. These numbers are 30 for ${\mathrm{Pb}}_n$, 20 for ${\left(\mathrm{NaI}\right)}_n$ and 52 for ${\mathrm{Xe}}_n$. The two positive charges generated at one atom by electron bombardment are likely to move to opposite sides of the cluster which then explodes into singly charged fragments as long as the Coulomb repulsion energy is greater than the binding energy.

The first exact solution of the time-dependent Debye-Smoluchowski equation for diffusional drift under a general interaction in the presence of a reactive sink is presented. Associated time-dependent rates of chemical reactions in a dense gas are formulated and display the basic physical transition from reaction control to transport control as time progresses for a system initially in Boltzmann equilibrium.

Photon-echo interference damping and anomalous coherent Raman beats are observed due to the spin-rotation interaction from laser-excited vibration-rotation transitions in ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$${\mathrm{H}}_3$F at 9.6μm. Pulsed Stark fields superimposed upon a constant magnetic field control the intrinsic mixture of spin-rotation states. The spin-rotation interaction for spin $I=\frac{1}{2}$ is confirmed from photon-echo measurement and theory.

We have demonstrated a pulsed two-photon laser at the transition $3d{}_{}{}^2{}_{}{}^{}D-2s{}_{}{}^2{}_{}{}^{}S$ of atomic Li (frequency ${\omega }_{31}$) by (i) generation of a coherent light beam at ${\omega }_x$, stimulated by light pulses at ${\omega }_1={\omega }_{31}-{\omega }_x$, and (ii) single-pass amplification of injected light at ${\omega }_3=\frac{{\omega }_{31}}{2}$.

Theoretical results are reported for energy propagation in bounded spatially dispersive (exciton-polariton) media. A remarkable slowing down of the energy-transport velocity $V_E$ is predicted near resonance. For GaAs the decrement is by a factor of ${10}^4$, with $V_E\sim 4\times {10}^3$ m/sec at resonance. Some comparison is made between energy-transport, group, and signal velocities, and available data.

The Helmholtz force density ${\overrightarrow{\mathrm{f}}}^{\left(\mathrm{H}\right)}$ for a dielectric fluid placed in an electric field is derived microscopically. It is found that in addition to an electrical force, there is also an additional mechanical force proportional to $\overrightarrow{\mathrm{E}}$ and only the sum of the two equals ${\overrightarrow{\mathrm{f}}}^{\left(\mathrm{H}\right)}$. Time-dependent cases are briefly discussed.

A perturbation calculation shows that the power spectrum of strange attractor near the accumulation parameter of a period-doubling bifurcation sequence consists of peaks broadened by a phase modulation, with broad skirts created by an amplitude modulation. Moving toward the accumulation parameter, at each bifurcation the total noise power decreases by a factor of 10.48, the average peak width decreases by a factor of 20.96, and the spectral bandwidth of the skirts decreases by a factor of 2.

Shear Alfvén waves accompanied by a broad spectrum of magnetic fluctuations are observed to be destabilized by a weak field-aligned current, and resultant strong plasma diffusion is caused. The instability with frequencies much higher than an electron diamagnetic drift frequency is considered to be driven by a resistivity gradient and current in a finite-$\beta$ plasma.

Monte Carlo calculations of the free energy of argon clusters are presented. The resulting homogeneous nulceation rates are in reasonable agreement with the experimental data over a wide range of pressures (${10}^{-4\mathrm{}} \mathrm{atm}<p<\mathrm{}2\mathrm{}\times {10}^{-1\mathrm{}} \mathrm{atm}$) and temperatures ($25°\mathrm{K}<T<\mathrm{}60\mathrm{}°\mathrm{K}$) at the onset of condensation.

We consider a system of fermions interacting via both strong spin-conserving and weak (spin-nonconserving) magnetic dipole forces. An expression for the spin relaxation rate $\frac{1}{T_1}$ in terms of the incoherent dynamic structure factor $S_I(q,\omega )$ is derived by treating the dipole interaction as a perturbation. We have calculated $T_1$ for normal liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ at all temperatures using the polarization-potential approach of Aldrich and Pines as well as the measured spin-diffusion coefficient and find good agreement with available data.

A ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ Mössbauer study of LiTa${\mathrm{O}}_3$ in the temperature range from 4.2 to 1050 K reveals temperature-induced changes of the electronic structure. Both the electric-field-gradient tensor and the total electron density at the nucleus exhibit dramatic temperature dependences. The latter reflects a charge transfer from the neighboring O ions to the central Ta ion increasing nonlinearly with temperature, an effect that has been postulated theoretically on the basis of a nonlinear anisotropic polarizability of the O ion.

We present experimental measurements of the resonance of the large intensity dependence of refractive index in InSb near the band-gap energy at 77 K and derive a semiempirical theory for this effect which fits the measurements well, both in absolute magnitude and wavelength dependence, using only measurable parameters. The size of the effect in other nondegenerate direct-band-gap III-V compound semiconductors and at other temperatures is predicted.

The phase diagram of the infinite-range model of spin-glasses exhibits two mixed phases. In these mixed phases, ferromagnetism and spin-glass order coexist, due to freezing of the transverse degrees of freedom or replica symmetry breaking. This may help to interpret a number of recent experimental findings, e.g., in $\mathrm{Au}\mathrm{Fe}$.

X-ray photoelectron spectra of Ag, O, and Cs and quantum yield distributions from surfaces prepared by evaporating Cs onto Ag oxidized in ultrahigh vacuum have been measured. The structure of this surface determined from these measurements consists of silver particles dispersed in a matrix of ${\mathrm{Cs}}_2$O with a layer of ${\mathrm{Cs}}_{11}$${\mathrm{O}}_3$ on top. The threshold at 1.2 μm is due to a lowering of the surface barrier by the ${\mathrm{Cs}}_{11}$${\mathrm{O}}_3$ and the yield in the visible and near infrared is explained as due to the excitation of Mie or optical resonance absorption in the silver particles.

Tunneling characteristics of junctions of the form $\mathrm{Al}{\mathrm{O}}_x$-Pd-Pb are reported. From the thickness dependences of $T_c$ and the induced gaps we find that the total BCS interaction ($\mathrm{NV}$) in Pd is 0±0.05. We find a Fermi velocity of ∼ 0.2×${10}^8$ cm/sec indicating that the narrow $d$-band electrons dominate our measurements. Pd phonon structure is not resolved, setting an upper limit of $\lambda \lesssim 0.2$ for the effective electron-phonon interaction. These results indicate that paramagnon effects are substantially less important for superconductivity than was previously envisioned.

A conservative transport operator in ($r$,$v_{\parallel }$,$v_{\perp }$) space and moment equations are derived which describe the combined effects of a stochastic magnetic field and a radial electric field on the electrons. The transport operator is coupled with Fokker-Planck and Ohmic-heating terms to compute the distribution function. A physical picture emerges which emphasizes the possible importance of the ambipolar potential ($\sim \frac{T_e}{e}$) and plasma boundary physics in determining overall plasma confinement.

A sound-velocity variation as a function of the acoustic power is reported. This variation is observed in amorphous PdSi at 10 mK for 500-MHz shear waves. It is shown that the transverse relaxation time $T_2$ of the tunneling defects can be deduced from this effect. A very short value $T_2=2\mathrm{}$ nsec is thus obtained in PdSi. It is then confirmed by a hole-burning experiment.

The dynamic structure factor of entangled polymer chains in a melt is investigated by neutron spin-echo techniques and by computer simulations of related models. Over a wide range of wave vectors $q$ the structure factor decays with time $t$ exponentially with a rate $\propto q^2{t}^{\frac{1}{2}}$, in agreement with the simple Rouse model. Reptation is found to be effective only for simulations of chains in a frozen-in environment, under otherwise identical conditions.