[en] Stimulated Raman process is used to selectively pump a highly excited vibrational state in a molecular beam. Theoretical evaluation shows that continuous lasers with power of less than 1 W can efficiently pump a single rotational-vibrational level of many simple molecules. Characteristics of the selectively pumped molecular beam and operational conditions are discussed theoretically. The experiment on a Na2 beam is found to agree with theoretical predictions. A flux of 4 x 10 to the 7th/s in the v = 31, J = 5 excited level has been obtained with use of two CW dye lasers with powers of 80 and 300 mW. 33 references

[en] K beta X-ray lines from partially M-shell-ionized ions of titanium through nickel which are produced in vacuum-spark plasmas have been observed systematically for the first time, using a high-resolution curved-crystal spectrometer. Each K beta line is clearly separated into its corresponding charge state. As a result, it is possible to measure the K beta-type transition energies of the M-shell-ionized ions. The transition energies accurately determined are compared with those calculated for iron ions, and the agreement is excellent except for ions having some additional 3d outer-shell electrons or 3s inner-shell vacancies. The square root of the K beta transition frequency is expressed as a linear function of the nuclear charge for isoelectronic sequences. The effective nuclear charges have been also determined for each K beta transition. The 3p electrons do not affect the effective nuclear charges. 10 references

[en] We clarify the assumptions involved in our analysis of the Rayleigh-Taylor instability in a spherical geometry published recently

[en] Our earlier measurements of K-shell photoelectric cross sections for intermediate Z elements at 74 and 37 keV have been extended to 26 keV using external conversion x rays in Sn. The experimental results are found to show fairly good agreement with the theoretical values of Scofield

[en] The aerothermodynamic studies of proposed space missions require atmospheric charge-transfer data. N2(+) eigenstate energies are calculated with use of the complete-active-space self-consistent-field method with an extended Gaussian basis set. The N(+)-N charge-exchange cross section, determined from these energies, agrees with merged-beam measurements. This contradicts the previous theoretical conclusion. A simple physical description of the long-range interaction is presented and should expedite future charge-transfer studies. 12 references

[en] The threshold photoionization method was used to study low-energy electron attachment phenomena in and cross sections of CCl4 and SF6 compounds, which have applications in the design of gaseous dielectrics and diffuse discharge opening switches. Measurements were made at electron energies from below threshold to 140 meV at resolutions of 6 and 8 meV. A narrow resolution-limited structure was observed in electron attachment to CCl4 and SF6 at electron energies below 10 meV, which is attributed to the divergence of the attachment cross section in the limit epsilon, l approaches zero. The results are compared with experimental collisional-ionization results, electron-swarm unfolded cross sections, and earlier threshold photoionization data. 34 refs

[en] A theory is developed for the interaction of coherent electromagnetic (EM) radiation with a free electron gas and for the influence of the plasma on the photon statistics of the radiation field. Two important possibilities for generating squeezed states are shown: squeezed states can be generated by the interaction of a one-mode laser with a plasma in a cavity; squeezed states can be generated by transmitting coherent radiation through the plasma. The maximal squeezing of the radiation obtained in the latter case is equal to the reciprocal of the dielectric constant of the plasma. Inside the plasma the EM field is represented by quasi-photons. Their dispersion relations are derived by using Bogoliubov transformations together with a self-consistency requirement for the motion of the electrons interacting with these quasi-photons. The squeezing processes are found to be strong when the frequency of the radiation is a little above the plasma frequency. By adding a constant magnetic field in the direction of propagation of the EM wave different amounts of squeezing are obtained for right- and left-circularly polarized EM waves. 28 references

[en] It has been proposed [J. L. Bobin, Opt. Commun. 55, 413 (1985)] that the presence of a plasma can, under certain conditions, enhance the accelerating electric field in an inverse free-electron laser. In this scheme, the beat wave generated by a laser and an undulator is expected to couple to the plasma oscillations generated by the electron beam streaming through the plasma. We have undertaken an analytical and numerical study of the proposed acceleration scheme. Our results show that the electric field is dominantly the self-field of the electron beam, and the plasma makes a negligible contribution to the electric field. Based on our analysis, we propose an alternative method of acceleration that employs a high-current electron beam to generate a beat wave that is subsequently used to accelerate a higher-energy beam. We show that an accelerating electric field ∼1 MeV/cm can be achieved with an electron beam of current density ∼20 kA/cm². The results of the analytical study agree well with numerical results from a two-dimensional computer code. The parameters of a proof-of-principle experiment are presented

[en] We employ a parameter-free positron-correlation-polarization (PCOP) potential to calculate total (rotationally summed) cross sections for the positron-H₂ (N₂) collisions below the positronium formation threshold energy. A laboratory frame close-coupling technique, retaining six rotational states (j=0,2,4,6,8,10), has been used. It is found that the PCOP model compares reasonably well with measured values. Results on rotationally elastic and inelastic cross sections are also reported. We also make a comparison between PCOP and electron-correlation-polarization models for all the cross sections reported here

[en] A measurement of the doubly differential cross sections of secondary electrons ejected from molecular oxygen by electron impact has been made. A modulated crossed-beam method was used with incident electron energies from 25 to 250 eV. The energy and angular range of secondary electrons covered from 1.0 eV to one-half of the difference between the incident energy and ionization potential and from 12 degree to 156 degree, respectively. The present results have been compared with the previous measurements and considerable discrepancies were found