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Research paper thumbnail of Electro-impact Excitation of the 4S 2D and 4S 2s2P 4P

Research paper thumbnail of X-Ray Emissions from Collisions of O 6+ Ions with Co

The Astrophysical Journal, 2011

ABSTRACT

Research paper thumbnail of High-Voltage Square-Wave Generator

Fast switching circuit puts out rectangular pulses of order of kilovolt or greater at typical rep... more Fast switching circuit puts out rectangular pulses of order of kilovolt or greater at typical repetition frequencies as high as hundreds of kilohertz and with rise times as short as 50 ns. Designed around power metal oxide/semiconductor field-effect transistors (MOSFET's). Optically isolated power MOSFET's in series rapidly switch output between high voltages V(sub 1) and V(sub 2). Used to supply power to pulsed laser or to modulate beam of charged particles in laboratory experiment or industrial process.

Research paper thumbnail of Electron Excitation Cross Sections for the 3s(sup 2)(sup 2) 3P 3s3p(sup 3) (sup 5)S Transition in S(sup 2

Research paper thumbnail of Measurements and Theoretical Predictions of Charge Exchange Cross Sections and Emission Spectra for O6+with H2O, CO, CO2, CH4, N2, NO, N2O and Ar

Journal of Physics: Conference Series, 2015

Synopsis Relevant to modeling and understanding X-ray emission from cometary and planetary atmosp... more Synopsis Relevant to modeling and understanding X-ray emission from cometary and planetary atmospheres, total charge-exchange cross sections for 1.17 and 2.33 keV/u O 6+ ions colliding with H2O, CO, CO2, CH4, N2, NO, N2O, and Ar have been measured and calculated for the processes of single, double, and triple exchanges. Synthetic emission spectra spanning the X-ray, UV, and visible ranges have also been calculated, based on theoretical treatment of the transfer of between one and six electrons from the target neutral to the projectile ion, followed by radiative and nonradiative decay of the resulting highly-excited projectile states.

Research paper thumbnail of The puzzling detection of x-rays from Pluto by Chandra

Using Chandra ACIS-S, we have obtained low-resolution imaging X-ray spectrophotometry of the Plut... more Using Chandra ACIS-S, we have obtained low-resolution imaging X-ray spectrophotometry of the Pluto system in support of the New Horizons flyby on 14 July 2015. Observations were obtained in a trial “seed” campaign conducted in one visit on 24 Feb 2014, and a follow-up campaign conducted soon after the New Horizons flyby that consisted of 3 visits spanning 26 Jul to 03 Aug 2015. In a total of 174 ksec of on-target time, in the 0.31 to 0.60 keV passband, we measured 8 total photons in a co-moving 11 × 11 pixel2 box (the 90% flux aperture determined by observations of fixed background sources in the field) measuring ∼121,000 × 121,000 km2 (or ∼100 × 100 RPluto) at Pluto. No photons were detected from 0.60 to 1.0 keV in this box during the same exposures. Allowing for background, we find a net signal of 6.8 counts and a statistical noise level of 1.2 counts, for a detection of Pluto in this passband at > 99.95% confidence. The Pluto photons do not have the spectral shape of the backg...

Research paper thumbnail of Chemical sensor system

Research paper thumbnail of Chemical sensor system

Research paper thumbnail of Lifetimes of the2s22p2Po–2s2p24Pintercombination transitions ofC+

Research paper thumbnail of Experimental-theoretical comparisons of 11S→31P differential magnetic sublevel cross sections for electron-helium scattering at 80 and 100 eV

Journal of Physics B: Atomic and Molecular Physics

Research paper thumbnail of Experimental-theoretical comparisons of 11S to 21P differential magnetic sublevel cross sections for electron-helium scattering at 60 eV and 80 eV

Journal of Physics B: Atomic and Molecular Physics

Research paper thumbnail of X-ray emission from electron capture by highly-charged ions

AIP Conference Proceedings

Research paper thumbnail of Electron-ion collision studies using a 14.0 GHz ECRIS

AIP Conference Proceedings, 1999

Research paper thumbnail of Absolute, cascade-free cross sections for the S→2P transition in Zn+ using electron-energy-loss and merged-beams methods

Physical Review Letters, 1991

Research paper thumbnail of Measurement of Lifetimes and f-Values in Multiply-Charged Positive Ions

Research paper thumbnail of Intensity Measurements in the B3Pi0+u- X1Sigma0+g System of l2

Research paper thumbnail of MEASUREMENT AND CALCULATION OF ABSOLUTE SINGLE AND MULTIPLE CHARGE EXCHANGE CROSS SECTIONS FOR Fe {sup q} {sup +} IONS IMPACTING HO

Research paper thumbnail of Experimental Cross Sections for Excitation of the 2s S-2 yields 2p P-2 Transition in C(3+)

Research paper thumbnail of Recent Excitation, Charge Exchange, and Lifetime Results in Highly Charged Ions Relevant to Stellar, Interstellar, Solar and Comet Phenomena

Research paper thumbnail of Intensity Measurements in the B3P0+u - X 1S0+g System of I2

Research paper thumbnail of Electro-impact Excitation of the 4S 2D and 4S 2s2P 4P

Research paper thumbnail of X-Ray Emissions from Collisions of O 6+ Ions with Co

The Astrophysical Journal, 2011

ABSTRACT

Research paper thumbnail of High-Voltage Square-Wave Generator

Fast switching circuit puts out rectangular pulses of order of kilovolt or greater at typical rep... more Fast switching circuit puts out rectangular pulses of order of kilovolt or greater at typical repetition frequencies as high as hundreds of kilohertz and with rise times as short as 50 ns. Designed around power metal oxide/semiconductor field-effect transistors (MOSFET's). Optically isolated power MOSFET's in series rapidly switch output between high voltages V(sub 1) and V(sub 2). Used to supply power to pulsed laser or to modulate beam of charged particles in laboratory experiment or industrial process.

Research paper thumbnail of Electron Excitation Cross Sections for the 3s(sup 2)(sup 2) 3P 3s3p(sup 3) (sup 5)S Transition in S(sup 2

Research paper thumbnail of Measurements and Theoretical Predictions of Charge Exchange Cross Sections and Emission Spectra for O6+with H2O, CO, CO2, CH4, N2, NO, N2O and Ar

Journal of Physics: Conference Series, 2015

Synopsis Relevant to modeling and understanding X-ray emission from cometary and planetary atmosp... more Synopsis Relevant to modeling and understanding X-ray emission from cometary and planetary atmospheres, total charge-exchange cross sections for 1.17 and 2.33 keV/u O 6+ ions colliding with H2O, CO, CO2, CH4, N2, NO, N2O, and Ar have been measured and calculated for the processes of single, double, and triple exchanges. Synthetic emission spectra spanning the X-ray, UV, and visible ranges have also been calculated, based on theoretical treatment of the transfer of between one and six electrons from the target neutral to the projectile ion, followed by radiative and nonradiative decay of the resulting highly-excited projectile states.

Research paper thumbnail of The puzzling detection of x-rays from Pluto by Chandra

Using Chandra ACIS-S, we have obtained low-resolution imaging X-ray spectrophotometry of the Plut... more Using Chandra ACIS-S, we have obtained low-resolution imaging X-ray spectrophotometry of the Pluto system in support of the New Horizons flyby on 14 July 2015. Observations were obtained in a trial “seed” campaign conducted in one visit on 24 Feb 2014, and a follow-up campaign conducted soon after the New Horizons flyby that consisted of 3 visits spanning 26 Jul to 03 Aug 2015. In a total of 174 ksec of on-target time, in the 0.31 to 0.60 keV passband, we measured 8 total photons in a co-moving 11 × 11 pixel2 box (the 90% flux aperture determined by observations of fixed background sources in the field) measuring ∼121,000 × 121,000 km2 (or ∼100 × 100 RPluto) at Pluto. No photons were detected from 0.60 to 1.0 keV in this box during the same exposures. Allowing for background, we find a net signal of 6.8 counts and a statistical noise level of 1.2 counts, for a detection of Pluto in this passband at > 99.95% confidence. The Pluto photons do not have the spectral shape of the backg...

Research paper thumbnail of Chemical sensor system

Research paper thumbnail of Chemical sensor system

Research paper thumbnail of Lifetimes of the2s22p2Po–2s2p24Pintercombination transitions ofC+

Research paper thumbnail of Experimental-theoretical comparisons of 11S→31P differential magnetic sublevel cross sections for electron-helium scattering at 80 and 100 eV

Journal of Physics B: Atomic and Molecular Physics

Research paper thumbnail of Experimental-theoretical comparisons of 11S to 21P differential magnetic sublevel cross sections for electron-helium scattering at 60 eV and 80 eV

Journal of Physics B: Atomic and Molecular Physics

Research paper thumbnail of X-ray emission from electron capture by highly-charged ions

AIP Conference Proceedings

Research paper thumbnail of Electron-ion collision studies using a 14.0 GHz ECRIS

AIP Conference Proceedings, 1999

Research paper thumbnail of Absolute, cascade-free cross sections for the S→2P transition in Zn+ using electron-energy-loss and merged-beams methods

Physical Review Letters, 1991

Research paper thumbnail of Measurement of Lifetimes and f-Values in Multiply-Charged Positive Ions

Research paper thumbnail of Intensity Measurements in the B3Pi0+u- X1Sigma0+g System of l2

Research paper thumbnail of MEASUREMENT AND CALCULATION OF ABSOLUTE SINGLE AND MULTIPLE CHARGE EXCHANGE CROSS SECTIONS FOR Fe {sup q} {sup +} IONS IMPACTING HO

Research paper thumbnail of Experimental Cross Sections for Excitation of the 2s S-2 yields 2p P-2 Transition in C(3+)

Research paper thumbnail of Recent Excitation, Charge Exchange, and Lifetime Results in Highly Charged Ions Relevant to Stellar, Interstellar, Solar and Comet Phenomena

Research paper thumbnail of Intensity Measurements in the B3P0+u - X 1S0+g System of I2

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