9,061 research outputs found
Shape-resonance-induced non-FranckāCondon effects in (2+1) resonance enhanced multiphoton ionization of the C 3Ī g state of O2
We show that strong non-FranckāCondon effects observed in (2+1) resonance enhanced multiphoton ionization of the C 3Pig state of O2 are due to the ksigmau shape resonance previously observed in single-photon studies of diatomic molecules. Calculated vibrational branching ratios for the v=2,3 levels of the C 3Ī g state are in reasonable agreement with experiment. Certain discrepancies remain in comparing theoretical results with the measured spectra, and possible electron-correlation effects which underly this are discussed
A recurrence matrix method for the analysis of longitudinal and torsional vibrations in non-uniform multibranch beams with variable boundary conditions
An approximate method for calculating the longitudinal and torsional natural frequencies and associated modal data of a beamlike, variable cross section multibranch structure is presented. The procedure described is the numerical integration of the first order differential equations that characterize the beam element in longitudinal motion and that satisfy the appropriate boundary conditions
Vibrational state dependence of ionic rotational branching ratios in resonance enhanced multiphoton ionization of CH
We show that rapid evolution of a Rydberg orbital with internuclear distance in a resonance enhanced multiphoton ionization (REMPI) process can have a profound influence on the production of molecular ions in alternative rotational states. This is illustrated by calculations of ionic rotational branching ratios for (2+1ā²) REMPI via the O11 (20.5) branch of the Eā²ā^2Ī£^+(3pĻ) Rydberg state of CH. The rotational propensity rule for ionization changes from ĪN=odd (ĪN=N_+āN_i) at lower vibrational excitation, as expected from the ĪN+l=odd selection rule, to ĪN=even at higher vibrational levels. This effect is expected to be quite general and should be most readily observable in diatomic hydrides
Theoretical performance of cross-wind axis turbines with results for a catenary vertical axis configuration
A general analysis capable of predicting performance characteristics of cross-wind axis turbines was developed, including the effects of airfoil geometry, support struts, blade aspect ratio, windmill solidity, blade interference and curved flow. The results were compared with available wind tunnel results for a catenary blade shape. A theoretical performance curve for an aerodynamically efficient straight blade configuration was also presented. In addition, a linearized analytical solution applicable for straight configurations was developed. A listing of the computer program developed for numerical solutions of the general performance equations is included in the appendix
Abundance of low energy (50-150 MeV) antiprotons in cosmic rays
The progress is presented of the nuclear emulsion experiment to determine abundance of low energy antiprotons in cosmic rays. No antiprotons have been detected so far at upper limit of p/p less than or similar to 4 x .0001 in the energy range 50 MeV to 15 MeV
The baboon endogenous virus genome. II. Provirus sequence variations in baboon cell DNA
Restriction analysis of the approximately 100 integrated baboon endogenous virus (BaEV) proviruses in baboon cells and tissues has revealed two major sequence variations, both in the gag gene region of the genome. One, a 150 nucleotide pair insert, is present in a small proportion of the proviral DNAs of some baboons, but is present in the majority of the proviral DNAs of other baboons. The second, a Bam HI recognition sequence located 2.25 kb from the proviral 5' end, is missing or modified in approximately one-half of the integrated genomes. We consider the possibility that accumulation of proviruses not containing the 0.15 kb insert is correlated with viral activation and expression since it is this form that is a replication intermediate in freshly infected permissive cells. It is evident from these initial studies that the organization of the multiple BaEV proviruses in baboon DNA has undergone modification during evolution
Shape resonance and non-FranckāCondon effects in (2+1) resonant enhanced multiphoton ionization of O_2 via the C3Ī g state
We report vibrationally resolved photoelectron angular distributions for photoionization of the C3Ī g Rydberg state of O2. Comparison is made with recent experimental measurements of angular distributions which employ (2+1) resonant enhanced multiphoton ionization of the C3Ī g state. The present theory treats the process as single-photon ionization from an unaligned Rydberg state, and qualitatively accounts for much of the observed trends. Non-FranckāCondon effects induced by the kĻu shape resonance lead to a substantial dependence of the angular distributions on the vibrational state of the X2Ī g ion. Discrepancies between our theoretical results and experiment are qualitatively discussed and tentatively attributed to residual electron correlations
Accuracy threshold for concatenated error detection in one dimension
Estimates of the quantum accuracy threshold often tacitly assume that it is
possible to interact arbitrary pairs of qubits in a quantum computer with a
failure rate that is independent of the distance between them. None of the many
physical systems that are candidates for quantum computing possess this
property. Here we study the performance of a concatenated error-detection code
in a system that permits only nearest-neighbor interactions in one dimension.
We make use of a new message-passing scheme that maximizes the number of errors
that can be reliably corrected by the code. Our numerical results indicate that
arbitrarily accurate universal quantum computation is possible if the
probability of failure of each elementary physical operation is below
approximately 10^{-5}. This threshold is three orders of magnitude lower than
the highest known.Comment: 7 pages, 4 figures, now with error bar
Photoionization of the 3Ļ and 1Ļ orbitals of CH
We report the results of theoretical studies of photoionization cross sections and photoelectron angular distributions for the 3Ļ and 1Ļ levels of CH leading to the Aā^1Ī , a ^3Ī , and Xā^1Ī£^+ molecular ions. The calculations employed multipletāspecific HartreeāFock potentials and numerical photoelectron continuum orbitals, obtained using the iterative Schwinger variational method. Noticeable nonstatistical behavior of the cross sections is seen for the 3Ļ level near threshold, although deviations are not significant at higher photon energies. A comparison with some previous theoretical studies is made
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