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Samson, J. A. R.

Publications and source records attributed to Samson, J. A. R..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Vacuum ultraviolet photoelectron spectroscopy of atoms and molecules

For a complete study of the photoionization of atoms and molecules it is essential to make use of the technique of Photoelectron Spectroscopy and the continuum characteristics of synchrotron radiation. A brief review is given of the application of the above techniques in measuring partial photoionization cross sections and the angular distribution assymetry parameter beta. Selected results are given, which are compared to theoretical values.

Samson, J. A. R.↗
NASA NTRS1978

Vibrational intensity distributions for the various electronic states of O2/+/, N2/+/ and CO/+/ produced by photoionization

Vibrational intensity distributions obtained with many discrete emission lines are presented for all major electronic states of O2(+), N2(+) and CO(+) subjected to photoionization. The vibrational distributions are reported as a function of wavelength between 745 and 304 A. The data, provided by photoelectron spectroscopy with an electron energy analyzer of known luminosity, appear to be consistent with calculated Franck-Condon Factors. Evidence for autoionization in the data is also discussed.

Gardner, J. L.↗
NASA NTRS1978

Polarized vacuum ultraviolet and X-radiation

The most intense source of polarized vacuum UV and X radiation is synchrotron radiation, which exhibits a degree of partially polarized light between about 80-100%. However, the radiation transmitted by vacuum UV monochromators can also be highly polarized. The Seya-Namioka type of monochromator can produce partially polarized radiation between 50-80%. For certain experiments it is necessary to know the degree of polarization of the radiation being used. Also, when synchrotron radiation and a monochromator are combined the polarization characteristic of both should be known in order to make full use of these polarization properties. The polarizing effect of monochromators (i.e., diffraction gratings) have been measured at the Seya angle and at grazing angles for various spectral orders. Experimental evidence is presented which shows that the reciprocity law holds for polarization by reflection where the angle of incidence and diffraction are unequal. These results are reviewed along with the techniques for measuring the degree of polarization.

Samson, J. A. R.↗
NASA NTRS1977

Double ionization of CO2 by photon impact

Double ionization of CO2 by photon impact from the double-ionization threshold at energies of 36.2 eV (342 A) to 110 eV (113 A) has been observed. The ratio of doubly to singly charged ions shows a linear rise with photon energy for approximately 15 eV above the threshold and reaches a constant value of about 2% between 67 and 110 eV.

Samson, J. A. R.↗
NASA NTRS1977

The vibrational energy levels and dissociation energy of O2/+/ /X 2 Pi g/

The absolute vibrational energy levels of the X 2 Pi g state of O2(+) have been determined by the method of photoelectron spectroscopy in the range nu = 0-25. The precision of the method is comparable to that of conventional high resolution optical spectroscopy. The dissociation energy obtained by a linear extrapolation of the vibrational separations is found to be 6.67 plus or minus 0.18 eV.

Samson, J. A. R.↗
NASA NTRS1976

Photoionization of atoms and molecules

A literature review on the present state of knowledge in photoionization is presented. Various experimental techniques that have been developed to study photoionization, such as fluorescence and photoelectron spectroscopy, mass spectroscopy, are examined. Various atoms and molecules were chosen to illustrate these techniques, specifically helium and xenon atoms and hydrogen molecules. Specialized photoionization such as in positive and negative ions, excited states, and free radicals is also treated. Absorption cross sections and ionization potentials are also discussed.

Samson, J. A. R.↗
NASA NTRS1976

Vibrational intensity distributions in the photoelectron spectrum of hydrogen

The intensity distribution over the H2(+) vibrational levels up to a vibrational quantum number of 15 has been measured for H2 photoelectron spectra at a photon wavelength of 584 A. The data show reasonable agreement with recent calculations only in the range of vibrational quantum numbers from 0 through 8; the higher levels are populated significantly lower than predicted by theory.

Gardner, J. L.↗
NASA NTRS1976

Calibration of electron-energy spectrometers

Relative photoionization cross-sections of strong peaks in the He(I) photoelectron spectra of N2, CO, CO2, and O2 are tabulated. These data have been measured with an electron energy analyzer whose relative luminosity has been calibrated to an accuracy of + or - 5%. Thus, the tables will be useful for calibrating the transmission of other analyzers for electron energies below 9 eV. Correction for angular distribution effects is discussed.

Gardner, J. L.↗
NASA NTRS1976

Angular distribution of photoelectrons at 584 A using polarized radiation

Photoelectron angular distributions for Ar, Xe, N2, O2, CO, CO2, and NH3 have been obtained at 584 A by observing the photoelectrons at a fixed angle and simply rotating the plane of polarization of a highly polarized photon source. The radiation from a helium dc glow discharge source was polarized (84%) using a reflection type polarizer

Hancock, W. H.↗
NASA NTRS1975

A calibration of detectors and gratings between 100 and 600 Angstroms

Calibration and efficiency measurements of magnetic electron multipliers, diffraction gratings, and photocathodes over the wavelength range 100 to 600 A are reported. For some of the measurements it was found necessary to use the synchrotron radiation from a storage ring. Measurements of grating efficiencies, the polarization produced by diffraction gratings, and the photoelectric yields of various photocathodes are included.

Samson, J. A. R.↗
NASA NTRS1975

Vibrational intensity distributions in the photoelectron spectrum of hydrogen

The intensity distribution over the H2(+) vibrational levels up to a quantum number of 15 was measured for H2 photoelectron spectra at a photon wavelength of 584 A. The data show reasonable agreement with recent calculations only in the quantum number of 0 through 8. The higher levels are populated significantly lower than predicted by theory.

Gardner, J. L.↗
NASA NTRS1975

Transfer calibration of the transmission of electron-energy spectrometers

Relative intensities of strong peaks in the Hel photoelectron spectra of N2, CO2, CO, and O2 are tabulated. These data were measured with an electron energy analyzer whose relative transmission was calibrated to an accuracy of + or - 5%. The tables are useful for calibrating the transmission of other analyzers for electron energies below 9 eV. Correction for angular distribution effects is discussed.

Gardner, J. L.↗
NASA NTRS1975

Collecting efficiency of a cylindrical mirror electron energy analyzer with pre-retarding lens

The electron collecting efficiency of a cylindrical mirror energy analyzer incorporating retardation of the electrons prior to analysis has been determined over the range 0 to 30 eV by two methods. The first method requires the use of a vacuum ultraviolet monochromator to produce monoenergetic electrons of different energies; the second method involves measuring the energy-brightness relationship of the retarding optics and should be applicable to any deflection analyzer with pre-retarding optics. The results of the two methods are compared and the limitations of the latter method are discussed.

Gardner, J. L.↗
NASA NTRS1975

Angular distribution of photoelectrons at 584A using polarized radiation

Photoelectron angular distributions for Ar, Xe, N2, O2, CO, CO2, and NH3 were obtained at 584 A by observing the photoelectrons at a fixed angle and simply rotating the plane of polarization of a highly polarized photon source. The radiation from a helium dc glow discharge source was polarized (84%) using a reflection type polarizer.

Hancock, W. H.↗
NASA NTRS1974

Vibrational intensity distributions for continuum photoionization of oxygen

The paper reports on experimental vibrational intensity distributions for continuum photoionization of oxygen using both 584 and 304 A helium lines. A cylindrical mirror energy analyzer with known transmission properties was used to record photoelectron spectra at a resolution of 45 meV with dispersed He radiation. At each wavelength the vibrational intensity distribution were corrected for the transmission of the analyzer and normalized to 100 at the strongest level. A table lists the results with calculated Franck-Condon factors.

Gardner, J. L.↗