The L x-ray spectrum of indium has been measured in fluorescence by using a double-crystal spectrometer. The relative energies, relative intensities, and the natural widths of the diagram lines are determined and compared to the theoretical calculations as well as x-ray photoemission spectroscopy data. The results show that the energies of transitions involving $L_1$, $M_2$,3, and $N_1$ shells are shifted 3–9 eV from the theoretical self-consistent-field energies. There also exists a discrepancy in the theoretical and experimental linewidths of these transitions. The cause of these effects is discussed.

An experimental investigation of the spectrum of x rays emitted in the electron-capture decay of ${}_{}{}^{163}{}_{}{}^{}\mathrm{Ho}$ is described. The data obtained are analyzed to determine their sensitivity to the value of the neutrino mass. At a 95% confidence level, an upper limit of 225 eV is set for the electron neutrino mass. No evidence for a finite value is found. Using available photon detectors, further improvements of this result are severely limited by uncertainties in atomic interference effects inherent to the decay.

The technique of Doppler-free two-photon spectroscopy was used to measure rates for line broadenings and frequency shifts of Rydberg levels with pressure. Measurements were made of spectra of ${}_{}{}^2{}_{}{}^{}\mathrm{S}$ and ${}_{}{}^2{}_{}{}^{}\mathrm{D}$ states (with n∼10–40) for ${\mathrm{Rb}}^{\mathrm{*}\mathrm{*}}$+Rb and ${\mathrm{K}}^{\mathrm{*}\mathrm{*}}$+K, and of ${}_{}{}^2{}_{}{}^{}\mathrm{S}$ states (with n=14–29) for ${\mathrm{K}}^{\mathrm{*}\mathrm{*}}$+Rb. Large oscillations are observed in both broadening and shift rates for n∼20–30 in all series except for the ${}_{}{}^2{}_{}{}^{}\mathrm{D}$ series in ${\mathrm{Rb}}^{\mathrm{*}\mathrm{*}}$+Rb. Overall rates for broadening and shift are compared with a theory based on the ‘‘free-electron’’ model. The observed oscillations are inconsistent with theories based on the resonance scattering of the Rydberg electron by the perturbing atom. A possible alternative mechanism related to interference in l-mixing collisions is suggested.

The traveling-molecular-orbital-expansion description has been employed to investigate electron capture in collisions of fully stripped ions (Z=6–9) with H and ${\mathrm{H}}_2$ in the energy regime from 0.14 to 9 keV/amu. The pseudopotential method was used to represent the ${\mathrm{H}}_2$${\mathrm{}}^{+}$ core which enables us to treat the ${\mathrm{H}}_2$ molecule as an atom having an ionization potential for ${\mathrm{H}}_2$→${\mathrm{H}}_2$${\mathrm{}}^{+}$. Features of the adiabatic potentials and corresponding radial coupling matrix elements at the ‘‘reaction window’’ as well as the quantitative results of relatively small-scale close-coupling calculations provide a rationale for the interpretation of a recent measurement for these systems by Meyer et al. [Phys. Rev. A 32, 3310 (1985)]. For collisions of ${\mathrm{O}}^{8+}$ with H, an extended molecular-orbital-expansion approach has been employed (i) to seek an understanding of the discrepancy evident in two recent independent large-scale calculations for n=6 partial cross sections, and (ii) to obtain a quantitative test for the mechanism suggested in this paper.

Solid hydrogen crystals of both para and normal species were grown in a glass cell 6.4 cm long and 1.0 cm in diameter using liquid-helium cryogenics apparatus. Their infrared-absorption spectra were recorded in the first overtone region 8000–9400 ${\mathrm{cm}}^{\mathrm{-}1}$. The absolute intensities of several zero-phonon transitions of the type $Q_2$(J), $Q_1$(J)+$Q_1$(J), $S_2$(J), $Q_2$(J)+$S_0$(J), $Q_1$(J)+$S_1$(J), $S_2$(J)+$S_0$(J), and $S_1$(J)+$S_1$(J) and those of the accompanying phonon branches $Q_R$ and $S_R$ were measured. The observed spectra clearly demonstrate that there is no contribution to the intensity of the pure overtone $Q_R$ phonon branch from isotropic electron overlap induction mechanism. This is in striking contrast to the observations in the fundamental band of either solid [H. P. Gush, W. F. J. Hare, E. J. Allin, and H. L. Welsh, Can. J. Phys. 38, 176 (1960)] or gaseous [S. P. Reddy, G. Varghese, and R. D. G. Prasad, Phys. Rev. A 15, 975 (1977)] hydrogen.

Pulse propagation in a vacuum is described as being the superposition of elementary pulses given by the time derivative of the initial pulse and weighted by local inclination factors attached to the pulse wave front. Optical pulses with any wave-front profile and propagating in near-field and far-field regions are considered. The analytical expressions thus obtained demonstrate the possibility to compute the pulse structure as a function of time and its evolution through numerical simulations.

A new method to measure picosecond or subpicosecond vibrational-dephasing dynamics with the use of incoherent or broadband light is presented theoretically and experimentally. It is based on a transient coherent Raman process with three beams. In our experimental scheme, two of them are incoherent light from a single source, and a delay time between the two is variable. A third beam has a higher frequency than the incoherent light by a vibrational energy in a molecule of interest, and is coherent in the delay-time range of the measurement. The delay-time dependence of coherent Stokes Raman scattering (CSRS) intensity offers the information about the coherence dynamics of the vibrational transition with a resolution time determined only by the correlation time of the incoherent light. For the theoretical calculation, a three-level model of the molecular system with homogeneous broadening is used, and delay-time dependences of the CSRS signal are calculated for off-resonance and resonance cases. Dephasing dynamics of the 2915-${\mathrm{cm}}^{\mathrm{-}1}$ mode in dimethylsulfoxide was observed experimentally by the new method with the use of nanosecond laser pulses, and the result agrees well with that obtained with picosecond pulses.

The nonclassical distance of a state of the electromagnetic field is defined. This distance allows one to say how nonclassical a given state is and places bounds on the extent to which the behavior of that state can deviate from that of classical states. Methods are developed for estimating nonclassical distance and are applied to number states and squeezed states.

This paper presents a calculation of the depth of the saturation dip observed when laser radiation of a Gaussian ${\mathrm{TEM}}_{00}$ mode is absorbed in a thermal molecular beam or in a very-low-pressure gas. Transit-time broadening is assumed to be the only broadening mechanism, with neglect of collisions and other relaxations. There is no restriction to small saturation parameters. The absorption experienced by one molecule has been calculated via the optical Bloch equations. Averaging over all relevant parameters of the molecular trajectory and the laser field followed. To get a reference for the saturation, from which to measure the dip depth, simply twice the absorption from a running-wave field has been taken, which therefore also had to be calculated in addition to the calculation of the absorption in a standing wave. Preliminary experiments have been carried out for comparison, and the data agree very well with the calculated shape of the curve and the absolute values of the calculated dip depth. From the laser-power scaling factor, necessary to fit the experimental data to the universal theoretical curve, the dipole moment can be derived without having to know such hard-to-determine quantities as absorber density, partition function, collision relaxation rate, or even the diameter of the laser beam.

We report the observation of a colored-noise-induced first-order nonequilibrium phase transition in a single-mode dye laser. Although a second-order phase transition exists in the more usual single-mode laser models, the order of the phase transition can be altered by including colored-noise fluctuations in the pumping of the laser. The nonwhite character of the noise is shown to be crucial to the onset of the characteristics of a first-order phase transition.

A theory of the quantum-beat laser is developed using a general Fokker-Planck approach. An explicit expression for the diffusion coefficient for the relative phase angle of the two modes is derived. It is shown that the diffusion coefficient can vanish under certain conditions.

Spectroscopic laser photodetachment of ${\mathrm{O}}_3$${\mathrm{}}^{\mathrm{-}}$ is accomplished in a drift tube with mass and mobility identification in the photon energy range from 2.0 to 4.7 eV. The initial ionic state is in the electronic and vibrational ground state. The photodetachment cross section of ${\mathrm{O}}_3$${\mathrm{}}^{\mathrm{-}}$ is found to increase with the photon energy at a rate of about 1.25×${10}^{\mathrm{-}18}$ cm ${\mathrm{eV}}^{\mathrm{-}1}$, with the threshold at 2.082±0.040 eV. The bond length and the bond angle of ${\mathrm{O}}_3$${\mathrm{}}^{\mathrm{-}}$ are determined through Franck-Condon factor analysis to be r=1.3415±0.0300 Å and theta=112.6±2.0°. .AE

We prove that the transition to a convective pattern in a Rayleigh-Bénard cell with a step in the heat input can be obtained by restricting the system to the locally attractive and locally invariant center manifold in phase space. The problem of providing the adequate scaling factor for the random source in the order-parameter equation is solved and the theoretical findings reproduce satisfactorily the experimentally measured time dependence for the convective heat flow.

Plasma relaxation, as well as the relaxation of more general diffusive systems, is discussed from a dynamical point of view. It is shown that a state which minimizes the rate of entropy production, as suitably defined, attracts neighboring states and thus causes relaxation. For plasmas, the entropy principle is compared with Taylor’s hypothesis of energy minimization and is shown to explain observed experimental results. An iteration scheme based on the entropy principle is constructed, and enables numerical calculation of the relaxed state. The scheme arises more naturally than the ‘‘local potential’’ method of Glansdorff and Prigogine which is improved upon.

A new kind of thermal plasma device has been constructed consisting of an indirectly heated 2100 K X-band microwave cavity. The cavity is filled with a surface ionized K or Cs plasma with densities of from 1×${10}^{16}$ to 1×${10}^{17}$ ${\mathrm{m}}^{\mathrm{-}3}$. As a first experiment, the frequency of the ${\mathrm{TM}}_{010}$ mode has been measured as a function of microwave power absorbed by the cavity. The measurements are carried out under conditions where instabilities are not observed in the plasma. The resonant frequency is found to decrease as the microwave power increases. Two theories are developed to explain the frequency shifts, one depending on the ponderomotive force, the other on high-frequency resistive electron heating. Frequency shifts predicted by the ponderomotive force theory are substantially smaller than the observed shifts. The data are in reasonable agreement with the resistive-electron-heating theory if it is assumed that the work function of the microwave cavity wall is decreased by alkali-metal-atom coverage.

Absorption studies of the high-n Rydberg states of ${\mathrm{CH}}_3$I perturbed by varying number densities of He, Ne, Ar, and Kr (up to 23.0, 24.0, 11.3, and 6.6×${10}^{20}$ ${\mathrm{cm}}^{\mathrm{-}3}$, respectively) are reported. Energy shifts, which increase with increasing perturber number density, are observed and analyzed for both discrete [nd${(}^2$$E_{3/2}$)] and autoionizing [nd’${(}^2$$E_{1/2}$)] states. These shifts vary linearly with the perturber number density for principal quantum numbers n≥10. Moreover, depending upon the nature of the perturber, these shifts are to the blue region (He), slightly to the blue region (or nearly zero) (Ne), or the red region (Ar and Kr). We explain these results quantitatively on the basis of the electron scattering length in the various rare gases, as well as on the polarization of the medium by ${\mathrm{CH}}_3$${\mathrm{I}}^{+}$. For low perturber number densities, it is well known that the Fermi model of perturber effects on high-n Rydberg states is invalid. The present experimental results show, for the first time, that this model also fails at high number densities. On the other hand, the energy shifts can be reproduced quantitatively by extending a model developed by Alekseev and Sobel’man to high number densities.

Morriss and Evans recently developed a generalization of the Green-Kubo relations which is valid for nonequilibrium steady states far from equilibrium. This formalism relates the nonequilibrium response to transient time correlation functions which connect the nonequilibrium steady state to the equilibrium state. In the linear regime, the transient time correlation functions reduce to simple equilibrium Green-Kubo relations. The transient time correlation function method thus provides a long-sought-after fundamental relation between nonequilibrium molecular dynamics algorithms and the Green-Kubo formalism which is only valid close to equilibrium. In this paper we demonstrate the use of the transient time correlation function formalism for isothermal planar Couette flow. The results show that the nonlinear steady-state response can be calculated by integrating the appropriate transient response time correlation function. In particular, the nonlinear shear stress and pressure calculated in this way agree with the values calculated directly.

The plasma maser theory of Langmuir waves produced from interaction between ion-wave turbulence and electrons in magnetized plasma is presented. The most dominant destabilizing effect comes from the polarization term. The instability occurs even for the Maxwell electron distribution function. The importance of the magnetic field for the plasma maser theory is stressed.

Macroscopic variables of the macroscopic system lose the quantum fluctuations in the macroscopic limit. A separate Hilbert space corresponds to each c-number value of these macroscopic variables. The measuring process in quantum mechanics consists of recording these c-number values and amounts to determination of the Hilbert space to which the system belongs. These observations provide a solution to the problem of measurement and lead to predictions concerning the c-number equations of motion of the macroscopic variables.

The atomic properties and transition probabilities of highly ionized aluminum in hot, dense plasmas were studied. In particular, we present computational results of the variations with density of the following atomic parameters: atomic potential and screening factor (due to both bound and free electrons), free-electron distribution, atomic wave functions, binding energies, line shifts, and, finally, transition probabilities and oscillator strengths. The calculations were carried out using the ion-sphere model (ISM) which treats the bound and free electrons in the atom self-consistently in a central potential. This potential is produced by the combination of the nuclear Coulomb field together with contributions by the bound- and free-electron charge distributions. The results indicate an increasing effect of the plasma on the atomic properties with increasing plasma density. Particularly, the free-electron screening reduces the atomic potential, pushes the atomic wave functions away from the nucleus, and reduces the binding energy of the bound electrons. The transition probability also decreases monotonically with density up to the ionization limit of the upper state beyond which it drops to zero. The computational results are compared to those expected from a homogeneous free-electron spatial distribution.