The $2^{-}$ level in ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ at the threshold for the reaction ${}_{}{}^7{}_{}{}^{}\mathrm{Li}\mathrm{}(p,n)\mathrm{}{}_{}{}^7{}_{}{}^{}\mathrm{Be}$ is shown to be a virtual state relative to threshold. A description of the state as an $S$-matrix pole in the scattering-length approximation gives a good account of its properties as observed in different reaction channels, and, in particular, removes an apparent contradiction about its width as observed through particle and $\gamma$-ray channels. The width of the $2^{-}$ state is found to be about 50 keV.

The reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(e,e^{\prime }p)$ at 497 MeV in conjunction with a distorted-wave impulse-approximation analysis was used to determine kinetic and separation energies of bound protons. The spectral function for separation energies less than 74 MeV provides only hal of the total binding energy; i.e., the data do not satisfy Koltun's sum rule. The momentum distributions are compatible with elastic electron scattering.

Bound and continuum properties of the system ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}+n$ are obtained from a microscopic model by means of an extended $R$-matrix formalism. The model includes configurations arising from excitation of up to four particles from the closed ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ core and provides a useful dynamical description of the observed low-energy spectrum.

Differential cross sections for $K^{-}p\to {\overline{K}}^{0}n$ and $K^{+}n\to K^{0}p$ have been measured at 3, 4, and 6 GeV/c using a data sample of 6000 events. Contrary to simple exchange-degenerate models, the ratio of $K^{+}$ to $K^{-}$ cross sections was found to be approximately 1.35, with little dependence on either $s$ or $t$. Both reactions show a shallow dip near the forward direction, suggesting the importance of spin-flip amplitudes.

Data obtained in a ${\pi }^{+}p$ backward-elastic-scattering experiment from 2 to 6 GeV/c were used to investigate $s$-channel ${\Delta }^{++}$ resonances between 2170 and 3490 MeV/${\mathit{c}}^2$. Two different models for fitting the energy dependence of ${\left(\frac{d\sigma }{d\Omega }\right)}_{180°}$ gave good fits. We present values for the masses, widths, parities, and the product of the spin and elasticity for the $\Delta \mathrm{}\left(2420\right)\mathrm{}$, $\Delta \mathrm{}\left(2850\right)\mathrm{}$, and $\Delta \mathrm{}\left(3230\right)\mathrm{}$ as well as the recently observed negative-parity resonance at ∼2200 MeV/${\mathit{c}}^2$.

Total cross sections for nucleon-$\alpha$ and $\alpha \alpha$ collisions are calculated for $86<s<\mathrm{}2776\mathrm{}$ ${\mathrm{GeV}}^2$ in the Glauber approximation. The results are compared with those obtained by assuming factorization for the Pomeron. Calculations for $s>\mathrm{}2776\mathrm{}$ ${\mathrm{GeV}}^2$, with simple assumptions regarding nucleon-nucleon elastic collisions, are also given. For $100<s<\mathrm{}2776\mathrm{}$ ${\mathrm{GeV}}^2$, where $\mathrm{NN}$ data exist, the Glauber-approximation results differ from the factorization predictions by ∼ 4-10%. At higher energies the factorization predictions are approached slowly.

${\mathrm{Ne}}^{+}$ ions of 235 and 363 keV primary energy are scattered from a dilute Ne gas target. Ne $K$ x rays excited in these collisions are detected in coincidence with ions scattered through laboratory angles ranging from 3 to 36°. The impact-parameter dependence of inner-shell excitation thus derived matches well with the Briggs-Macek theory.

A microwave-optical pulsing and trapping technique has been employed to observe Lamb-shift ($\mathcal{S}=2\mathrm{}{S}_{\frac{1}{2}}\to 2P_{\frac{1}{2}}$) transitions in ${}_{}{}^6{}_{}{}^{}\mathrm{Li}_{}^{2+}{}_{}{}^{}$. Microwave transitions were induced in trapped metastable ${\mathrm{Li}}^{2+}\left(2\mathrm{}{S}_{\frac{1}{2}}\right)$ ions produced beforehand by a pulsed electron beam incident upon a low-pressure lithium vapor. Resonances were observed in the soft x-ray decay light as an applied magnetic field was swept through the Zeeman transition frequency. Computer fitting of 76 line centers yields $\mathcal{S}=62765\mathrm{}\pm 21$ MHz in good agreement with theory.

60-MeV I ions were injected into the open (111) planar channels of thin Au single crystals. Characteristic I and Au $M$ x rays excited in the crystal were measured in coincidence with the transmitted ions. The ion energy identified their oscillation amplitude in the channel; this allowed determination of the impact-parameter dependence of x-ray excitation in small-angle collisions.

I report the observation of population inversion by optical adiabatic rapid passage. These observations, on an ${\mathrm{NH}}_3$ infrared transition with all the relevant parameters known, agree with theoretical expectations. The pressure dependence of $T_1$, obtained by this technique, makes possible the first estimate of the collision-induced rotational lifetime of ${\mathrm{NH}}_3$ in an excited band, which is significantly longer than the rotational lifetime in the ground vibrational band.

In a plasma with a magnetic field, a plasmon can decay into two electromagnetic waves: a left-hand-polarized electromagnetic wave and right-hand-polarized whistler wave, both propagating in the direction of the magnetic field. Use of this process for a plasma laser is discussed.

A new type of exciter consisting of electron beams for launching electron plasma waves is investigated experimentally and theoretically. When fast electron sheet beams, modulated at a prescribed frequency, are injected into plasmas, electron plasma waves are found to be excited nearly perpendicularly to the electron beams. Compared with a mesh excitation, we found that the beam excitation has several merits: it hardly excites ballistic modes, the direct coupling due to an electrostatic induction with another probe is small, and it can even be used in a very hot plasma.

We study the absorption of a ${\mathrm{CO}}_2$-laser beam by an independently produced plasma at approximately the critical density. The measured fractional absorption coefficient agrees with that associated with inverse breamsstrahlung for incident laser intensities below ${10}^{10}$ ${\mathrm{W}/\mathrm{c}\mathrm{m}}^2$. Above this value, an abrupt increase in absorption is observed.

A Monte Carlo calculation of the Feynman-Cohen excitation spectrum is performed for helium confined to two dimensions. No approximations are used. Results for several different areal densities are compared with an exactly similar calculation in three dimensions. Among other results the roton gap is found to be significantly lower at corresponding densities in two dimensions, much smaller than previous estimates, and in substantial agreement with experiment.

A partially ionized helium plasma ($n_e=5\mathrm{}\times {10}^{13}$ ${\mathrm{cm}}^{-3\mathrm{}}$) was heated by an intense ($\frac{\nu }{\gamma }\simeq 1$) relativistic electron beam (600 keV, 25-60 kA). Observations of the emitted line radiation and Thomson-scattered light indicate noncollisional electron heating rates consistent with electron-ion instability predictions, and total energy deposition consistent with electron-electron- instability saturation levels.

The temperature dependence of the electrical resistivity of ${\mathrm{Pd}}_{60}$${\mathrm{Ag}}_{40}$ between 4.2 and 900 K is shown to contain the same anomalies as previously found in Ni-Cu alloys in the midrange of composition. For Pd-Ag these effects cannot be due to scattering at giant polarization clouds, and are attributed to a temperature-dependent decrease of the impurity resistivity due to a reduction in $s-d$ scattering with increasing temperature.

We report a study of the temperature dependence of the $2k_{\mathrm{F}}$ instability in the one-dimensional conductor ${\mathrm{K}}_2$Pt${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4$${\mathrm{Br}}_{0.30}$${\mathrm{·}3\mathrm{D}}_2$O using a neutron scattering technique. Whereas the extra scattering at room temperature has a one-dimensional character corresponding to a periodicity along the $C$ axis of 6.66 Pt-Pt spacings, below 220 K it indicates the development of a three-dimensional superlattice structure with a new unit cell $2a\times 2a\times 6.66c$. However, this transition seems to be incomplete, in the sense that the coupling between adjacent chains does not achieve long-range order.

The angular distribution of the elastic-scattering differential cross section of 1.05-GeV protons by ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ has been measured from 3 to 47° lab. The main features of this measurement are that the first minimum is much less deep than previously measured and that, at the point where a second minimum is predicted by calculations, there is just a slight change of slope.

Ground-state bands up to $8^{+}$ and negative-parity bands, in one case up to ${15}^{\mathrm{═}}$, have been established in ${}_{}{}^{190,192,194}{}_{}{}^{}\mathrm{Hg}$ using ($\alpha ,xn$) reactions. Corresponding bands have been observed in ${}_{}{}^{191,193}{}_{}{}^{}\mathrm{Hg}$ and are interpreted as Coriolis-decoupled bands.

The reaction ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}(t,{}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ has been performed at a bombarding energy of 23.5 MeV. A number of low-lying $1^{+}$ states are observed in the spectrum of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ and these are related by the Coulomb energy difference to their analog $1^{+}$, $T=1\mathrm{}$ states which comprise the giant $M1\mathrm{}$ resonance structure of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. Of particular importance, the ($t,{}_{}{}^3{}_{}{}^{}\mathrm{He}$) strength distribution to the $1^{+}$ states in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ largely reproduces the distribution of electromagnetic transition rates of their analogs in Si. This provides strong evidence for the existence of the charge-exchange mode with $\Delta T_z=1\mathrm{}$ of the giant $M1\mathrm{}$ resonance in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$.