Electron impact cross sections for atmospheric species. I.
Electron impact cross sections used to determine helium collision cross sections sets
IONIZATION CROSS SECTION↗
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Ionization of ions
Charged particle binary encounter model modified for evaluating ionization cross section of positive ions by electron impact
Garcia, J. D.↗
The Pioneer 8 cosmic dust experiment.
Cosmic dust particle direction, velocity and mass from ionization and momentum measurements by dust sensor during impact on Pioneer 8 satellite
Berg, O. E.↗
Minima in generalized oscillator strengths for initially excited hydrogen-like atoms
Generalized oscillator strengths for transitions from an initially excited state of a hydrogenic atom to final states (either discrete or continuum) have complicated structures, including minima and shoulders, as functions of the momentum transfer. Extensive calculations carried out in the present work have revealed certain systematics of these structures. Some implications of the minima to the energy dependence of the inner-shell ionization cross section of heavy atoms by proton impact are discussed.
Matsuzawa, M.↗
Improvements in Ionized Cluster-Beam Deposition
Lower temperatures result in higher purity and fewer equipment problems. In cluster-beam deposition, clusters of atoms formed by adiabatic expansion nozzle and with proper nozzle design, expanding vapor cools sufficiently to become supersaturated and form clusters of material deposited. Clusters are ionized and accelerated in electric field and then impacted on substrate where films form. Improved cluster-beam technique useful for deposition of refractory metals.
Fitzgerald, D. J.↗
Ionization of helium, neon, and nitrogen by helium atoms.
Ionization cross sections for helium and neon atoms and nitrogen molecules due to impact of helium atomic beam
HELIUM ATOM↗
Cross sections and rate coefficients for inelastic interactions of heavy particles
The existing analytical inelastic cross-sections for direct atom-atom ionizing collisions of Firsov (1959), Fleischmann et al. (1972), and Drawin (1968) are discussed. General analytical expressions for direct ionization cross-sections in atom-atom collisions are derived. The main advantage of the present cross-sections is their generality, simplicity, and overall accuracy, which is acceptable in most applications and is better than the overall accuracy of the cross-sections of Firsov, Fleischmann et al., and Drawin. The atom-atom interaction is considered as a superposition of all the pairwise interactions between the test particle and all the electrons of the outer nl shell of the target atom. Such a picture of atom-atom collision is acceptable at low- and medium-impact energies because then the electrons of the outer shell of the target atom are most likely the ones that get ionized. At high-impact energy, the picture becomes inaccurate because of strong overlapping of the atomic shells.
Kunc, J. A.↗
The potential impact of bystander effects on radiation risks in a Mars mission
Densely ionizing (high-LET) galactic cosmic rays (GCR) contribute a significant component of the radiation risk in free space. Over a period of a few months-sufficient for the early stages of radiation carcinogenesis to occur-a significant proportion of cell nuclei will not be traversed. There is convincing evidence, at least in vitro, that irradiated cells can send out signals that can result in damage to nearby unirradiated cells. This observation can hold even when the unirradiated cells have been exposed to low doses of low-LET radiation. We discuss here a quantitative model based on the a formalism, an approach that incorporates radiobiological damage both from a bystander response to signals emitted by irradiated cells, and also from direct traversal of high-LET radiations through cell nuclei. The model produces results that are consistent with those of a series of studies of the bystander phenomenon using a high-LET microbeam, with the end point of in vitro oncogenic transformation. According to this picture, for exposure to high-LET particles such as galactic cosmic rays other than protons, the bystander effect is significant primarily at low fluences, i.e., exposures where there are significant numbers of untraversed cells. If the mechanisms postulated here were applicable in vivo, using a linear extrapolation of risks derived from studies using intermediate doses of high-LET radiation (where the contribution of the bystander effect may be negligible) to estimate risks at very low doses (where the bystander effect may be dominant) could underestimate the true risk from low doses of high-LET radiation. It would be highly premature simply to abandon current risk projections for high-LET, low-dose radiation; however, these considerations would suggest caution in applying results derived from experiments using high-LET radiation at fluences above approximately 1 particle per nucleus to risk estimation for a Mars mission.
Non-NASA Center↗
Investigation of Recombination Processes In A Magnetized Plasma
Interplanetary travel requires propulsion systems that can provide high specific impulse (Isp), while also having sufficient thrust to rapidly accelerate large payloads. One such propulsion system is the Variable Specific Impulse Magneto-plasma Rocket (VASIMR), which creates, heats, and exhausts plasma to provide variable thrust and Isp, optimally meeting the mission requirements. A large fraction of the energy to create the plasma is frozen in the exhaust in the form of ionization energy. This loss mechanism is common to all electromagnetic plasma thrusters and has an impact on their efficiency. When the device operates at high Isp, where the exhaust kinetic energy is high compared to the ionization energy, the frozen flow component is of little consequence; however, at low Isp, the effect of the frozen flow may be important. If some of this energy could be recovered through recombination processes, and re-injected as neutral kinetic energy, the efficiency of VASIMR, in its low Isp/high thrust mode may be improved. In this operating regime, the ionization energy is a large portion of the total plasma energy. An experiment is being conducted to investigate the possibility of recovering some of the energy used to create the plasma. This presentation will cover the progress and status of the experiment involving surface recombination of the plasma.
Chavers, Greg↗
Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies. III. Results for the Seyfert 2 Galaxies Markarian 3, Markarian 78, and NGC 1068
Outflows of ionized gas driven by active galactic nuclei (AGN) may significantly impact the evolution of their host galaxies. However, determining the energetics of these outflows is difficult with spatially unresolved observations that are subject to strong global selection effects. We present part of an ongoing study using Hubble Space Telescope and Apache Point Observatory spectroscopy and imaging to derive spatially resolved mass outflow rates and energetics for narrow-line region outflows in nearby AGN that are based on multi-component photoionization models to account for spatial variations in gas ionization, density, abundances, and dust content. This expanded analysis adds Mrk 3, Mrk 78, and NGC 1068, doubling our earlier sample. We find that the outflows contain total ionized gas masses of M ≈ 10(exp 5.5)-10(exp 7.5) M⨀ and reach peak velocities of v ≈ 800-2000 km s(exp -1). The outflows reach maximum mass outflow rates of M(sub OUT) ≈ 3-12 M⨀ yr(exp -1) and encompass total kinetic energies of E ≈ 10(exp 54)-10(exp 56) erg. The outflows extend to radial distances of r ≈ 0.1-3 kpc from the nucleus, with the gas masses, outflow energetics, and radial extents positively correlated with AGN luminosity. The outflow rates are consistent with in situ ionization and acceleration where gas is radiatively driven at multiple radii. These radial variations indicate that spatially resolved observations are essential for localizing AGN feedback and determining the most accurate outflow parameters.
Active galaxies↗
Magnetic field and remanent magnetization effects of basin-forming impacts on the moon
Maps of the distribution of lunar surface magnetic fields produced by the electron reflection method have shown that the largest observed concentrations of lunar crustal magnetization occur antipodal (diametrically opposite) to four relatively young large impact basins: Imbrium, Orientale, Serenitatis, and Crisium. A model is proposed here for the formation of these magnetization concentrations (or 'magcons') in which the partially ionized vapor cloud produced in a hypervelocity (greater than 10 km/s) basin-forming impact expands around the moon forcing a preexisting ambient magnetic field to be concentrated for a brief (less than 1 day) time period in the antipodal zone. Acquisition of magnetic remanence during the period of compressed field amplification may occur by one of several mechanisms, such as shock remanence by impact of solid secondaries ejected from the basin-forming event. The model implies that basin-forming impacts have played a major role in determining the large-scale distribution of crustal magnetization detectable from lunar orbit.
Hood, L. L.↗
IONIZATION OF NITROGEN AND OXYGEN MOLECULES BY NITROGEN AND OXYGEN MOLECULES
Measurement of ionization cross sections for nitrogen and oxygen molecules on impact with other nitrogen and oxygen molecules
OXYGEN↗
Infrared Response of H2 to X-Rays in Dense Clouds
The excitation by X-rays and cosmic rays of molecular hydrogen in interstellar clouds is analyzed. We carried out detailed calculations of entry efficiencies in rovibrational levels of H2 following impact with fast electrons produced by X-ray ionization of the gas. The competing effect of collisional excitation, and quenching by the ambient gas is examined in detail. Up to date values for H-H2 collisional rate coefficients are adopted, and some derivations of H2-H2 rovibrational rate coefficients from existing literature data are proposed. Several models as a function of temperature, density, and ionization rate are presented. We found that H2 infrared emission in X-ray dominated regions (XDR) is potentially observable for temperatures and ionization rates lower than certain critical values (typically T < 1000 K and zeta/n(sub H) < 10(exp -15) cc/s where zeta is the ionization rate). At higher temperatures, collisional excitation by the ambient gas dominates the population of low vibrational levels, and at higher values of zeta/n(sub H) the abundance of H2 is negligible. If such conditions are satisfied, the resulting infrared emission spectrum can be used as a diagnostic of nearby X-ray sources such as in cooling flows in galaxy clusters, quasars, Seyfert galaxies and supernova remnants. The intensity ratio of the 2-1S(1) and 1-0S(1) lines measured for the Seyfert galaxy NGC 1275 is consistent with X-ray pumping.
Tine, S.↗
Electron Impact Excitation of Forbidden and Allowed Transitions in O(II)
The B-spline R-matrix method is used to investigate the electron impact excitation of forbidden and allowed transitions in singly ionized oxygen. The relativistic effects have been incorporated in the Breit-Pauli Hamiltonian. Flexible non-orthogonal sets of radial functions are used to obtain accurate target description and to represent the scattering functions. The 47 fine-structure levels of the 2s(sup 2)2p(sup 3), 2s2p(sup 4), 2s(sup 2)2p(sup 2)3s, 2s(sup 2)2p(sup 2)3p and 2s(sup 2)2p(sup 2)3d configurations have been included in the scattering calculation. A calculation with 62 levels in the close-coupling expansion using the Breit-Pauli R-matrix (BPRM) method with orthogonal radial functions has also been carried out to check electron correlation, relativistic and channel coupling effects. The present results are in good agreement with the previous 16-level BPRM calculation by Montenegro et a1 (2006 J. Phys. B: At. Mol. Opt. Phys. 39 1863-77) for the forbidden transitions, but differ from the 21-level BPRM calculation by McLaughlin and Bell (1998 J. Phys. B: At. Mol. Opt. Phys. 31 4317-29). Our cross sections for the first forbidden (sup 4)S(sup o)-(sup 2)D(sup o)and resonance (sup 4)S(sup o)-2s(sup 2)p(sup 4) (sup 4)P transitions are in reasonably good agreement with the electron energy-loss and merged-beams experiment.
Tayal, S. S.↗
Extreme Poleward Expanding Super Plasma Bubbles Over Asia-Pacific Region Triggered By Tonga Volcano Eruption During the Recovery-Phase of Geomagnetic Storm
The Tonga volcano eruption of 15 January 2022 unleashed a variety of atmospheric perturbations, coinciding with the recovery-phase of a geomagnetic storm. The ensuing thermospheric variations created rare display of extreme poleward-expanding conjugate plasma bubbles seen in the rate of total electron content index over 100–150°E, reaching ∼40°N geographic latitude. This is associated with fluctuations in FORMOSAT-7/COSMIC-2 (F7/C2) ion-density measurements and spread-F in ionograms. Preceding to this, an unusually strong pre-reversal enhancement (PRE) occurred in the global ionospheric specification (GIS) electron density profiles derived from F7/C2 observations. The GIS also revealed a decrease of equatorial ionization anomaly (EIA) crest density due to the storm impact. Reduced E-region conductivity by volcano-induced waves and enhanced F-region wind, further accelerated by reduced ion-drag over the EIA, apparently intensified the PRE. Accompanied with the strong PRE, volcano-induced seed perturbations triggered the super plasma bubble activity.
P. K. Rajesh↗
Space Weathering Investigations Enabled by NASA's Virtual Heliophysical Observatories
Structural and chemical impact of the heliospheric space environment on exposed planetary surfaces and interplanetary dust grains may be generally defined as space weathering . In the inner solar system, from the asteroid belt inwards towards the Sun, the surface regolith structures of airless bodies are primarily determined by cumulative meteoritic impacts over billions of years, but the molecular composition to meters in depth can be substantially modified by irradiation effects. Plasma ions at eV to keV energies may both erode uppermost surfaces by sputtering, and implant or locally produce exogenic material, e.g. He-3 and H2O, while more energetic ions drive molecular change through electronic ionization. Galactic cosmic ray ions and more energetic solar ions can impact chemistry to meters in depth. High energy cosmic ray interactions produce showers of secondary particles and energetic photons that present hazards for robotic and human exploration missions but also enable detection of potentially useable resources such as water ice, oxygen, and many other elements. Surface sputtering also makes ejected elemental and molecular species accessible for in-situ compositional analysis by spacecraft with ion and neutral mass spectrometers. Modeling of relative impacts for these various space weathering processes requires knowledge of the incident species-resolved ion flux spectra at plasma to cosmic ray energies and as integrated over varying time scales. Although the main drivers for investigations of these processes come from NASA's planetary science and human exploration programs, the NASA heliophysics program provides the requisite data measurement and modeling resources to enable specification of the field & plasma and energetic particle irradiation environments for application to space weather and surface weathering investigations. The Virtual Heliospheric Observatory (VHO), Virtual Energetic Particle Observatory (VEPO), Lunar Solar Origins Exploration (LunaSOX), and Space Physics Data Facility (SPDF) services now provide a wide range of inner heliospheric spacecraft data that can be applied to space weathering of potential exploration destinations including the Moon, asteroids, and the moons of Mars, as well to radiation hazard assessment for the spacecraft and human explorers. For example, the new VEPO service for time-averaging of multi-source ion flux spectra enables the specification of composite flux spectra from a variety of ongoing and legacy missions for applications to surface interaction modeling. Apollo to Artemis data resources of LunaSOX enable specific space weathering investigations for the Moon, while VHO more generally covers the space field and plasma environments of the inner and outer solar system from the sunward-most perihelia of the twin Helios spacecraft to the ongoing heliosheath passages of the twin Voyagers. Composite multi-source spectra from VEPO can also be applied to the continuing compilation of accumulated 1-AU fluence spectra, mostly contributed by solar wind plasma and energetic particle events, for determination of time-averaged particle compositional and kinetic energy output from the Sun and for modeling of long-term irradiation impacts on planetary surfaces.
Cooper, John F.↗
Hypervelocity impact effects on solar cells
One of the space hazards of concern is the problem of natural matter and space debris impacting spacecraft. This phenomena has been studied since the early sixties and a methodology has been established to determine the relative abundance of meteoroids as a function of mass. As the mass decreases, the probability of suffering collisions increases, resulting in a constant bombardment from particles in the sub-micron range. The composition of this 'cosmic dust' is primarily Fe, Ni, Al, Mg, Na, Ca, Cr, H, O, and Mn. In addition to mechanical damage, impact velocities greater than 5 k m/sec can produce shock induced ionization effects with resultant surface charging and complex chemical interactions. The upper limit of the velocity distribution for these particles is on the order of 70 km/sec. The purpose of this work was to subject samples from solar power arrays to debris flux typical of what would be encountered in space, and measure the degradation of the panels after impact.
Rose, M. Frank↗
Fullerenes in an impact crater on the LDEF spacecraft
The fullerenes C60 and C70 have been found to occur naturally on Earth and have also been invoked to explain features in the absorption spectra of interstellar clouds. But no definitive spectroscopic evidence exists for fullerenes in space and attempts to find fullerenes in carbonaceous chondrites have been unsuccessful. Here we report the observation of fullerenes associated with carbonaceous impact residue in a crater on the Long Duration Exposure Facility (LDEF) spacecraft. Laser ionization mass spectrometry and Raman spectroscopy indicate the presence of fullerenes in the crater and in adjacent ejecta. Man-made fullerenes survive experimental hypervelocity (approximately 6.1 km s-1) impacts into aluminium targets, suggesting that space fullerenes contained in a carbonaceous micrometeorite could have survived the LDEF impact at velocities towards the lower end of the natural particle encounter range (<13 km s-1). We also demonstrate that the fullerenes were unlikely to have formed as instrumental artefacts, nor are they present as contaminants. Although we cannot specify the origin of the fullerenes with certainty, the most plausible source is the chondritic impactor. If, alternatively, the impact produced the fullerenes in situ on LDEF, then this suggests a viable mechanism for fullerene production in space.
long duration↗