We have calculated the ionization rate of hydrogen by an intense electromagnetic field in the dipole approximation and in an approximation in which this field dominates the electron-proton interaction in intermediate states. We find the transition rate behaves as $E^{-1\mathrm{}}$ for linearly polarized fields and $E^{-2\mathrm{}}\ln E$ for circularly polarized fields where $E$ is the amplitude of the electric field. We have also calculated the transition rate for excitation of the $2s$ state and a Raman photon. The result behaves as ($E^{-2\mathrm{}}W$) for small $W$ where $W$ is the energy of the Raman photon. We estimate that the method is a good one for electric field strengths of the order of 2×${10}^{11}$ V/cm or higher. This is larger than available currently.

Production of Auger electrons from the Ar $L$ shell were studied in scattering experiments with 50- to 600-keV ${\mathrm{H}}^{+}$, ${\mathrm{D}}^{+}$, $\mathrm{H}_2^{}{}_{}{}^{+}$, and ${\mathrm{He}}^{+}$ impact on Ar. Electrons ejected at 150° with respect to the incident beam were measured using electrostatic parallel-plate spectrometers. Sets of electron spectra were acquired at different resolutions of 0.35-, 1.4-, and (1.7-2.4)-eV full width of half-maximum. Branching ratios for normal transitions from initial $L_2$ and $L_3$ vacancy states are compared with results of other authors. Satellite structures in the spectra are analyzed to determine probabilities for the excitation of multiple-vacancy states $L_{23}{M}^i$. Intensities of Auger electrons from the $L_1$ and $L_{23}$ shell are compared for an evaluation of the $L_1$-shell Coster-Kronig yield. Total cross sections for Ar $L$-shell ionization are obtained by integration of the Auger spectra and cross-section ratios are studied for ${\mathrm{He}}^{+}$ and ${\mathrm{D}}^{+}$ impact.

A $\frac{1}{Z}$ expansion method is used to calculate the eigenvalues and eigenfunctions for the ${\mathrm{}\left(1s\right)\mathrm{}}^{2}2s{}_{}{}^2{}_{}{}^{}S$ and ${\mathrm{}\left(1s\right)\mathrm{}}^{2}2p{}_{}{}^2{}_{}{}^{}P$ states of the lithium isoelectronic sequence. The dipole-length and dipole-velocity forms of the oscillator strengths for the $2s-2p$ resonance transitions are compared with the results of direct variational calculations for individual values of the nuclear charge $Z$. It is explicitly demonstrated that the length formulation of the dipole matrix element is more accurate than the velocity formulation for the $2s-2p$ transitions.

In the coupled-state impact-parameter method, the exact impact-parameter wave function is approximated by a trial impact-parameter wave function which is a finite linear combination of $N$ basis vectors with time-dependent coefficients. In the standard approach the coefficients are determined by solving the equations obtained by projecting the impact-parameter Schrödinger equation with the exact wave function replaced by the trial wave function onto the $N$ basis vectors which define the trial wave function. It is well known that this method gives variational estimates of the transition amplitudes if the basis vectors represent physical states. However, if in proton-hydrogen-atom scattering Sturmian basis vectors, which are for the most part nonphysical basis vectors, are used, the method is not variational. In this paper it is shown that if Sturmian basis vectors are used the method can be made variational by projecting the Schrödinger equation with the exact wave function replaced by the trial wave function onto the physical basis vectors of interest rather than onto the Sturmian basis vectors; the resultant equations are no more difficult to solve than the standard equations. It is also shown that useful variational bounds on the error of the estimate of a transition amplitude exist only if the trial wave function is expanded in terms of a physical basis set.

A test is made of the strength of the $G$-matrix condition and of the practicality of such numerical calculations. Results obtained show great improvement over previous results.

The interaction of the anomalous magnetic moments of neutrons in a hypothetical neutron halo with the muon-charge distribution in heavy muonic atoms is studied. We find large shifts in the $2p$ levels of the heaviest atoms. The shifts in the $3d$ level of Ba and in the $4f$ level of Pb are too small and of the wrong sign to account for the existing discrepancy in the vacuum-polarization corrections to these levels.

Self-consistent relativistic Dirac-Hartree-Fock calculations have been made of some lowlying electronic energies for the atoms of all elements in ground-state $d{s}^2$ electron configurations. The results indicate that, contrary to some previous estimates, the ground electronic state of atomic Lr could be in either the $5f^{14}6d7s^2$ or the $5f^{14}7p7s^2$ electron configuration. The separation between the lowest energy level of the $5f^{14}6d7s^2$ configuration and the lowest energy level of the $5f^{14}7p7s^2$ configuration is estimated to be (0 ± 3) × ${10}^3$ ${\mathrm{cm}}^{-1\mathrm{}}$ for atomic Lr.

The algebra of level splitting discovered by Biedenharn and Gamba is developed for the case SU(2) × SU(2)⊃SU(2). This is the physically interesting case to which much of conventional angular momentum theory is addressed. The interrelations of the two approaches are discussed in detail.

Intensities have been measured for 346 x-ray lines of kaonic atoms of elements and pure isotopes ranging from $Z=2\mathrm{}$ through $Z=92\mathrm{}$. Within experimental accuracy, isotopes of the same elements yielded equal intensities. However, a remarkable variation in intensities versus $Z$ was observed for kaonic transitions believed not to be significantly influenced by nuclear absorption. Fourteen x-ray lines from ${\Sigma }^{-}$-hyperonic atoms of light and medium-$Z$ elements were measured. Also observed were 29 nuclear $\gamma$-ray lines that followed kaon capture.

We study the finite transformation of the O(2,1) group associated with hydrogenic radial functions, and with its aid we evaluate atomic integrals $\int 0^{\infty }{R}_{\mathrm{ml}}\left(a_{m}r\right)R_{nl}\left(a_{n}r\right)r^{-1\mathrm{}}{e}^{-ikr}{r}^2\mathrm{dr},$ $\mathrm{Re}(ik+\frac{1}{2}{a}_m+\frac{1}{2}{a}_n)>\mathrm{}0,$ $\int 0^{\infty }{\left[R_{nl}\right(a_{n}r\left)\right]}^2{r}^{-1\mathrm{}}sin\mathrm{}\left(\mathrm{kr}\right)\mathrm{}{r}^2\mathrm{dr},$ $\int 0^{\infty }{\left[R_{nl}\right(a_{n}r\left)\right]}^2{r}^{-1\mathrm{}}cos\mathrm{}\left(\mathrm{kr}\right)\mathrm{}{r}^2\mathrm{dr},$ $\int 0^{\infty }{R}_{\mathrm{ml}}\left(a_{m}r\right)R_{nl}\left(a_{n}r\right)r^2\mathrm{dr},$ $\int 0^{\infty }{R}_{\mathrm{ml}}\left(a_{m}r\right)T{R}_{nl}\left(a_{n}r\right)r^2\mathrm{dr},$ where the functions $R_{nl}\left(a_{n}r\right)$ are the hydrogenic radial functions, and the operator $T$ represents the kinetic energy. The scale $a_m$ for each function can be chosen arbitrarily. Using some of these results, we obtain the two-particle radial integrals $\int 0^{\infty }{\left[R_{n{l}_1}\right(a{r}_1\left)\right]}^2{\left(r_1{r}_2\right)}^{-1\mathrm{}}\delta (r_1-r_2){\left[R_{n{l}_2}\right(a{r}_2\left)\right]}^2{r}_1^2{r}_2^{2}d{r}_{1}d{r}_2,$ $\int 0^{\infty }{\left[R_{n{l}_1}\right(a{r}_1\left)\right]}^2{\left(r_{>}\right)}^{-1\mathrm{}}{\left[R_{n{l}_2}\right(a{r}_2\left)\right]}^2{r}_1^2{r}_2^{2}d{r}_{1}d{r}_2.$

Absolute transition probabilities for 124 CI, SI, and SII lines in the range 3600-7400 ÅA are measured with a spectroscopic shock tube. Relative strengths of two CII lines are also determined. Mixtures of neon and ten different compounds of carbon and sulfur are heated to temperatures 8200-13000°K at pressures (4.8-27.0) × ${10}^6$ dyn ${\mathrm{cm}}^{-2\mathrm{}}$. Thermodynamic and photometric variables are measured redundantly. Absolute $A$ values are determined in emission by two or more independent methods which in combination have much less than the traditional sensitivity to systematic errors in source temperature. Estimated accuracies for the more prominent visible lines are 13-30%. Results are compared with theoretical predictions, other experiments, and with quantum-mechanical sum rules.

We report here a measurement of the lifetime of the first vibration state of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$F. The experiment was carried out using an electric-resonance molecular-beam technique and yielded the result ${\tau }_{10}={14.3}_{-2.1\mathrm{}}^{+2.7\mathrm{}}$ msec. This value is smaller than the prediction of Rittner's model and also smaller than estimates using existing spectroscopic data.

Laser-produced x-ray spectra of Sm, Gd, and Dy were measured in the energy range 800-2300 eV. Atomic self-consistent-field calculations were used to identify the transitions in ions stripped to the $M$ shell for the Gd spectra. This work extends the Ni I isoelectronic sequence to rare-earth elements.

The linked-cluster many-body perturbation theory is applied to the study of the one- and two-electron contributions to the magnetic contact, dipolar, and orbital hyperfine interaction in the $2{}_{}{}^3{}_{}{}^{}P$ state of the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}_{}^{+}{}_{}{}^{}$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}_{}^{+}{}_{}{}^{}$ ions. The relative importance of one- and two-electron contributions to the various hyperfine constants are discussed, and comparisons are made between our theoretical results and recent experimental data obtained both by beam-foil spectroscopy and by radio-frequency resonance techniques utilizing electron-impact excitation.

Using beam-foil excitation we have measured the absolute wavelengths of the transitions $3s{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}-3p{}_{}{}^3{}_{}{}^{}P_{0,1,2}^{}{}_{}{}^{}$ in N VI. The difference between the measured and calculated wavelength of the transition from ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ is atrributed to the sum of the Lamb shifts of the upper and lower levels. This sum is compared with the recent calculations of Ermolaev and tends to verify the unexpectedly large Lamb shift of the ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ level.

Photodetachment cross sections of ${\mathrm{C}}^{-}$ and ${\mathrm{F}}^{-}$ are calculated by means of the many-body perturbation theory with multiple basis sets. The $V^{N-1\mathrm{}}$ basis set is defined to include the intrachannel interaction. The $V^{N-2\mathrm{}}$ basis set is introduced to describe the correlation in the Hartree-Fock ground states of negative ions. The lowest-order cross sections agree very well with experiment. The first-order corrections are calculated in the case of ${\mathrm{F}}^{-}$, and a large cancellation is found between the initial-state correlation and the final-state interchannel interactions. The importance of the use of the energy relations in the lower-order calculations is pointed out.

Angular correlations between $K$ and $L$ x rays in ${}_{}{}^{245}{}_{}{}^{}\mathrm{Cm}$, ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$, and ${}_{}{}^{153}{}_{}{}^{}\mathrm{Eu}$ were measured. The x rays of Cm, Pu, and Eu were obtained from radioactive sources of 352-yr ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$, 32-yr ${}_{}{}^{243}{}_{}{}^{}\mathrm{Cm}$, and 242-day ${}_{}{}^{153}{}_{}{}^{}\mathrm{Gd}$, respectively. The $K$ x rays were detected with a cooled Ge(Li) spectrometer with energy resolution of 500-eV full width at half-maximum (FWHM) at 122 keV. The $L$ x rays were detected with a cooled Si(Li) spectrometer with energy resolution of 170 eV (FWHM) at 5.9 keV. Several corrections to the angular-correlation coefficients were made including a correction for the presence of silicon x-ray escape peaks. The corrected angular-correlation coefficients are:

The results for the $K{\alpha }_1-L\alpha$ cascades are in good agreement with theoretical predictions. The results for the $K{\alpha }_1-L\beta$ cascade agree with theory for Eu but deviate significantly from theory for Pu and Cm. The results for the $K{\alpha }_1-\mathrm{Ll}$ cascade in all three elements are lower than theoretical predictions. Results of similar studies of other elements are tabulated and compared to theory. For all elements studied the experimental angular-correlation coefficient agrees with the theoretical value for the $K{\alpha }_1-L\alpha$ cascade but is lower than the theoretical value for the $K{\alpha }_1-\mathrm{Ll}$ cascade.

We have observed stimulated light scattering from pure argon gas and argon gas with oxygen impurities (≤2%) in the gas density range of 30 to 350 amagat. By comparing our measured threshold laser power as a function of gas density with the corresponding theoretical values for stimulated thermal Rayleigh scattering (STRS), we identify the present scattering as STRS. We present arguments to show that the necessary absorption of laser light and subsequent thermalization which is essential for STRS can be provided by ${\mathrm{Ar}}_2^{*}$ molecules. These molecules are formed in the laser-produced plasma. The effect of small percentages of oxygen impurity in the argon gas seems to support this point of view.

The eikonal distorted-wave Born approximation developed recently by Chen, Joachain, and Watson is applied to hydrogen excitation by helium impact in the intermediate-energy range. The differential and total cross sections for the excitation of the hydrogen atom to the $2s$, $2p_{\pm }$, or $2p_0$ state by helium impact are presented. These results are compared to experiment and previous calculations. The differential cross section for the excitation of hydrogen to the $2s$ state compares well with the experimental data of Thomas and Sauers in shape and slope, but has a discrepancy in magnitude.

A molecular-beams apparatus is used in conjunction with a pulsed tunable uv laser to study the photoionization of argon and krypton $m{p}^5\left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right) \mathrm{}(m+1\mathrm{})\mathrm{}{s}^{\prime }:\left({}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}\right)$ and $m{p}^5\left({}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}\right) \mathrm{}(m+1\mathrm{})s:\left({}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}\right)$ metastable atoms in the wavelength range 3250-2690 Å. Major contributions to the ionization arise from excitation to $p^5\left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)n{f}^{\prime }$ and $p^5\left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)n{p}^{\prime }$ levels which autoionize into the underlying $P_{\frac{3}{2}}$ continuum. Term values are presented for these levels and compared with those calculated by extrapolation of the lower levels of these series, whose term values are known from spectroscopic observations. The widths of the autoionizing peaks are discussed together with the relative transition probabilities.