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Mark, H.

Publications and source records attributed to Mark, H..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The Space Station - Mankind's permanent presence in space

The present discussion is concerned with developments which led finally to the announcement of a new U.S. national commitment in January 1984. According to this announcement, plans are to be developed for the establishment of a permanently manned orbiting Space Station to be deployed within the decade. Early concepts regarding a space station go back to 1869, when a story was published in the 'Atlantic Monthly' about a large earth-orbiting sphere, built of brick, in which people lived and worked. Some decades later, the idea was taken up by Oberth in Germany and Tsiolkovsky in Russia. Their work had a decisive influence on Goddard in the U.S. and von Braun in Germany, who developed basic propulsion systems. Attention is given to rocket developments during and after the Second World War, the trip to the moon, the post-Apollo program, the Space Shuttle and the 1970's, planning for the Space Station, opposition to the Space Station, the Space Station debate, international and commercial interest, and the President's decision.

Mark, H.↗
NASA NTRS1984

Atomic inner-shell transitions

Atomic inner-shell processes have quite different characteristics, in several important aspects, from processes in the optical regime. Energies are large, e.g., the 1s binding energy reaches 100 keV at Z = 87; relativistic and quantum-electrodynamic effects therefore are strong. Radiationless transitions vastly dominate over photon emission in most cases. Isolated inner-shell vacancies have pronounced single-particle character, with correlations generally contributing only approximately 1 eV to the 1s and 2p binding energies; the structure of such systems is thus well tractable by independent-particle self-consistent-field atomic models. For systems containing multiple deep inner-shell vacancies, or for highly stripped ions, the importance of relativistic intermediate coupling and configuration interaction becomes pronounced. Cancellation of the Coulomb interaction can lead to strong manifestations of the Breit interaction in such phenomena as multiplet splitting and hypersatellite X-ray shifts. Unique opportunities arise for the test of theory.

Crasemann, B.↗
NASA NTRS1984

The management of research institutions: A look at government laboratories

Technology development; project management; employment patterns; research productivity; legal status of support services; functions of senior executives; the role of the sponsoring agency; research diversification; obstacles to technical innovation; organizational structures; and personnel management are addressed.

Mark, H.↗
NASA NTRS1983

Radiationless transitions to atomic M 1,2,3 shells - Results of relativistic theory

Radiationless transitions filling vacancies in atomic M1, M2, and M3 subshells have been calculated relativistically with Dirac-Hartree-Slater wave functions for ten elements with atomic numbers 67-95. Results are compared with those of nonrelativistic calculations and experiment. Relativistic effects are found to be significant. Limitations of an independent-particle model for the calculation of Coster-Kronig rates are noted.

Chen, M. H.↗
NASA NTRS1983

Relativistic calculation of atomic M-shell ionization by protons

Relativistic plane-wave Born-approximation calculations of cross sections for M-shell ionization of Ho-67, Au-79, U-92 by protons with incident energies from 0.05 to 1 MeV are reported. Dirac-Hartree-Slater wave functions were employed and binding-energy change and Coulomb deflection were taken into account. Associated X-ray production cross sections were also computed. Results are compared with previous theoretical predictions and with experimental data. Definite improvement in the theory has been attained by the use of realistic wave functions and consistent inclusion of the effects of relativity.

Chen, M. H.↗
NASA NTRS1980

Relativistic K-shell Auger rates, level widths, and fluorescence yields

Systematic relativistic (Dirac-Hartree-Slater) calculations of atomic K-shell Auger transition probabilities are reported for 25 elements with Z between 18 and 96, inclusive. K-level Auger widths are found to be enhanced by relativistic effects, while total K-level widths are reduced. Relativistic theoretical K-shell fluorescence yields are in excellent agreement with experiment. Theoretical relative intensities of K-LX Auger transitions in heavy elements, calculated in j-j coupling, agree well with measurements; for low Z, configuration interaction and intermediate coupling must apparently be included.

Chen, M. H.↗
NASA NTRS1980

Relativistic K-LL Auger spectra in the intermediate-coupling scheme with configuration interaction

Theoretical K-LL Auger spectra from relativistic Dirac-Hartree-Slater calculations in intermediate coupling with configuration interaction (ICWCI) are considered. Calculated transition rates for 25 elements with Z between 18 and 96, inclusive, are listed and compare well with experimental data. Relativistic effects are found to be important above Z equal to about 35, and ICWCI is necessary to describe the spectra for Z less than about 60.

Chen, M. H.↗
NASA NTRS1979

L-shell Auger and Coster-Kronig spectra from relativistic theory

The intensities of L-shell Auger and Coster-Kronig transitions in heavy atoms have been calculated relativistically. A detailed comparison is made with measured Auger spectra of Pt and U. The pertinent transition energies were computed from relativistic wave functions with inclusion of the Breit interaction, self-energy, a vacuum-polarization correction, and complete atomic relaxation. Multiplet splitting is found to distribute Auger electrons from certain transitions among several lines. The analysis leads to reassignment of a number of lines in the measured spectra. Lines originally identified as L2-L3Ni in the U spectrum are shown to arise from M4,5 Auger transitions instead.

Chen, M. H.↗
NASA NTRS1979

Relativistic L -shell Auger and Coster-Kronig rates and fluorescence yields

Relativistic calculations of radiationless transition rates to L -subshell vacancy states in selected atoms with Z in the 70-96 range have been performed. The Auger and Coster-Kronig transition probabilities are calculated from perturbation theory, assuming frozen orbitals, in the Dirac-Hartree-Slater approach. Transition rates, fluorescence yields, and Coster-Kronig yields are compared with nonrelativistic theoretical results and with experiment. Relativity is found to affect the L -subshell Auger widths by (10-25)% and individual transition rates to certain j-j configurations by as much as 40% at Z = 80. The widths of L sub i vacancy states and the L sub 2 Coster-Kronig yields f33 from these relativistic calculations agree much better with experiment than earlier nonrelativistic theoretical values.

Chen, M. H.↗
NASA NTRS1978

Exchange and relaxation effects in low-energy radiationless transitions

The effect on low-energy atomic inner-shell Coster-Kronig and super Coster-Kronig transitions that is produced by relaxation and by exchange between the continuum electron and bound electrons was examined and illustrated by specific calculations for transitions that deexcite the 3p vacancy state of Zn. Taking exchange and relaxation into account is found to reduce, but not to eliminate, the discrepancies between theoretical rates and measurements.

Chen, M. H.↗
NASA NTRS1977

Space Shuttle - A personal view

A typical flight profile for the Space Shuttle is reviewed, and the operation of the Spacelab, as well as deployment of a satellite from the Shuttle, is considered. Selection of crews for a Space Shuttle mission, which may include as many as four payload specialists, is also discussed. Since medical requirements and flight training standards need not be as high for payload specialists as for the three members of the flight crew, the Shuttle may provide an opportunity for many scientists to perform experiments in space. Investigations of the critical opalescence of fluids and laser holography are proposed for Shuttle missions; X-ray astronomy is another likely candidate for inclusion in the program.

Mark, H.↗
NASA NTRS1977

Interpretation of the silver L X-ray spectrum

Analysis of the Ag L-series X-ray spectrum has been performed, based on relaxed-orbital relativistic transition-energy calculations. Satellite energies were computed in intermediate coupling. It is found that satellites arising from LN double-hole states generally fall within the natural width of the parent diagram lines. Contrary to previous assumption, the observed high-energy satellites are due to LM double-hole states produced by L1-L3M4,5 Coster-Kronig transitions and by shakeoff. The observed peak structure in the satellite spectrum is due to multiplet splitting of the initial and final double-hole states. Theoretical L1-L3M4,5 transition rates based on the Coster-Kronig energies computed by Chen et al. (1977) are closer to experiment than previous results, but still are too large by a factor of about 2, indicating an as-yet undetected flaw in the theory.

Chen, M. H.↗
NASA NTRS1977

Atomic electron energies including relativistic effects and quantum electrodynamic corrections

Atomic electron energies have been calculated relativistically. Hartree-Fock-Slater wave functions served as zeroth-order eigenfunctions to compute the expectation of the total Hamiltonian. A first order correction to the local approximation was thus included. Quantum-electrodynamic corrections were made. For all orbitals in all atoms with 2 less than or equal to Z less than or equal to 106, the following quantities are listed: total energies, electron kinetic energies, electron-nucleus potential energies, electron-electron potential energies consisting of electrostatic and Breit interaction (magnetic and retardation) terms, and vacuum polarization energies. These results will serve for detailed comparison of calculations based on other approaches. The magnitude of quantum electrodynamic corrections is exhibited quantitatively for each state.

Aoyagi, M.↗
NASA NTRS1977

Interpretation of the silver L X-ray spectrum

Silver L X-ray energies were calculated using theoretical binding energies from relaxed orbital relativistic Hartree-Fock-Slater calculations. Theoretical X-ray energies are compared with experimental results.

Chen, M. H.↗
NASA NTRS1977

All-weather ice information system for Alaskan arctic coastal shipping

A near real-time ice information system designed to aid arctic coast shipping along the Alaskan North Slope is described. The system utilizes a X-band Side Looking Airborne Radar (SLAR) mounted aboard a U.S. Coast Guard HC-130B aircraft. Radar mapping procedures showing the type, areal distribution and concentration of ice cover were developed. In order to guide vessel operational movements, near real-time SLAR image data were transmitted directly from the SLAR aircraft to Barrow, Alaska and the U.S. Coast Guard icebreaker Glacier. In addition, SLAR image data were transmitted in real time to Cleveland, Ohio via the NOAA-GOES Satellite. Radar images developed in Cleveland were subsequently facsimile transmitted to the U.S. Navy's Fleet Weather Facility in Suitland, Maryland for use in ice forecasting and also as a demonstration back to Barrow via the Communications Technology Satellite.

Gedney, R. T.↗
NASA NTRS1976

Neutral-atom electron binding energies from relaxed-orbital relativistic Hartree-Fock-Slater calculations for Z between 2 and 106

Electron binding energies in neutral atoms have been calculated relativistically, with the requirement of complete relaxation. Hartree-Fock-Slater wave functions served as zeroth-order eigenfunctions to compute the expectation of the total Hamiltonian. A first-order correction to the local approximation was thus included. Quantum-electrodynamic corrections were made. For all elements with atomic numbers ranging from 2 to 106, the following quantities are listed: total energies, electron kinetic energies, electron-nucleus potential energies, electron-electron potential energies consisting of electrostatic and Breit interaction (magnetic and retardation) terms, and vacuum polarization energies. Binding energies including relaxation are listed for all electrons in all atoms over the indicated range of atomic numbers. A self-energy correction is included for the 1s, 2s, and 2p(1/2) levels. Results for selected atoms are compared with energies calculated by other methods and with experimental values.

Huang, K.-N.↗