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All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Effect of gravity on lung exhaled nitric oxide at rest and during exercise

Exhaled nitric oxide (NO) from the lungs (VNO) in nose-clipped subjects increases during exercise. This may be due to endothelial shear stress secondary to changes in pulmonary blood flow. We measured VNO after modifying pulmonary blood flow with head-out water immersion (WI) or increased gravity (2 Gz) at rest and during exercise. Ten sedentary males were studied during exercise performed in air and WI. Nine subjects were studied at 1 and 2 Gz. Resting NO concentrations in exhaled air ([NO]) were 16.3 +/- 8.2 ppb (air). 15 +/- 8.2 ppb (WI) and 17.4 +/- 5 ppb (2 Gz). VNO (ppb/min) was calculated as [NO]VE and was unchanged at rest by either WI or 2 Gz. VNO increased linearly with Vo2, VE and fii during exercise in air, WI and at 2 Gz. These relationships did not differ among the experimental conditions. Therefore, changes in pulmonary blood flow failed to alter the output of NO exhaled from the lungs at rest or during exercise.

Clinical Trial↗
NASA NTRS1997

Activation and proliferation of lymphocytes and other mammalian cells in microgravity

The experimental findings reviewed in this chapter support the following conclusions: Proliferation. Human T-lymphocytes, associated with monocytes as accessory cells, show dramatic changes in the centrifuge, in the clinostat and in space. In free-floating cells the mitogenic response is depressed by 90% in microgravity, whereas in cells attached to a substratum activation is enhanced by 100% compared to 1-G ground and inflight controls. The duration of phase G1 of the mitotic cycle of HeLa cells is reduced in hypergravity, resulting in an increased proliferation rate. Other systems like Friend cells and WI38 human embryonic lung cells do not show significant changes. Genetic expression and signal transduction. T-lymphocytes and monocytes show important changes in the expression of cytokines like interleukin-1, interleukin-2, interferon-gamma and tumor necrosis factor. The data from space experiments in Spacelab, Space Shuttle mid-deck, and Biokosmos have helped to clarify certain aspects of the mechanism of T-cell activation. Epidermoid A431 cells show changes in the genetic expression of the proto-oncogenes c-fos and c-jun in the clinostat and in sounding rockets. Membrane function, in particular the binding of ligates as first messengers of a signal, is not changed in most of the cell systems in microgravity. Morphology and Mortility. Free cells, lymphocytes in particular, are able to move and form aggregates in microgravity, indicating that cell-cell contacts and cell communications do take place in microgravity. Dramatic morphological and ultrastructural changes are not detected in cells cultured in microgravity. Important experiments with single mammalian cells, including immune cells, were carried out recently in three Spacelab flights, (SL-J, D-2, and IML-2 in 1992, 1993, and 1994, respectively). The results of the D-2 mission have been published in ref. 75; those of the IML-2 mission in ref. 76. Finally, many cell biology experiments in space have suffered in the past from a lack of adequate controls (like 1-G centrifuges) and of proper experimental conditions (like well-controlled temperature). In this respect the availability of Biorack, outfitted with proper incubators with 1-G control centrifuge as well as a glovebox with a microscope, is a great advantage. It is also desirable that cell biology experiments in space are accompanied or even preceded by a program of ground-based investigations in the fast rotating clinostat and in the centrifuge, and that preparatory experiments be done in parabolic flights and sounding rockets, whenever possible. Proper publication of the results of space experiments is another important need. A great number of data have been published in proceedings and reports that are not available to the broad scientific community. To guarantee the credibility and the international recognition of space biology it is important that the results be published in international, peer reviewed journals.

manned↗
NASA NTRS1997

Contractile properties of rat, rhesus monkey, and human type I muscle fibers

It is well known that skeletal muscle intrinsic maximal shortening velocity is inversely related to species body mass. However, there is uncertainty regarding the relationship between the contractile properties of muscle fibers obtained from commonly studied laboratory animals and those obtained from humans. In this study we determined the contractile properties of single chemically skinned fibers prepared from rat, rhesus monkey, and human soleus and gastrocnemius muscle samples under identical experimental conditions. All fibers used for analysis expressed type I myosin heavy chain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Allometric coefficients for type I fibers from each muscle indicated that there was little change in peak tension (force/fiber cross-sectional area) across species. In contrast, both soleus and gastrocnemius type I fiber maximal unloaded shortening velocity (Vo), the y-intercept of the force-velocity relationship (Vmax), peak power per unit fiber length, and peak power normalized for fiber length and cross-sectional area were all inversely related to species body mass. The present allometric coefficients for soleus fiber Vo (-0.18) and Vmax (-0.11) are in good agreement with published values for soleus fibers obtained from common laboratory and domesticated mammals. Taken together, these observations suggest that the Vo of slow fibers from quadrupeds and humans scale similarly and can be described by the same quantitative relationships. These findings have implications in the design and interpretation of experiments, especially those that use small laboratory mammals as a model of human muscle function.

NASA Discipline Musculoskeletal↗
NASA NTRS1996

Application of acute maximal exercise to protect orthostatic tolerance after simulated microgravity

We tested the hypothesis that one bout of maximal exercise performed at the conclusion of prolonged simulated microgravity would improve blood pressure stability during an orthostatic challenge. Heart rate (HR), mean arterial blood pressure (MAP), norepinephrine (NE), epinephrine (E), arginine vasopressin (AVP), plasma renin activity (PRA), atrial natriuretic peptide (ANP), cardiac output (Q), forearm vascular resistance (FVR), and changes in leg volume were measured during lower body negative pressure (LBNP) to presyncope in seven subjects immediately prior to reambulation from 16 days of 6 degrees head-down tilt (HDT) under two experimental conditions: 1) after maximal supine cycle ergometry performed 24 h before returning to the upright posture (exercise) and 2) without exercise (control). After HDT, the reduction of LBNP tolerance time from pre-HDT levels was greater (P = 0.041) in the control condition (-2.0 +/- 0.2 min) compared with the exercise condition (-0.4 +/- 0.2 min). At presyncope after HDT, FVR and NE were higher (P < 0.05) after exercise compared with control, whereas MAP, HR, E, AVP, PRA, ANP, and leg volume were similar in both conditions. Plasma volume (PV) and carotid-cardiac baroreflex sensitivity were reduced after control HDT, but were restored by the exercise treatment. Maintenance of orthostatic tolerance by application of acute intense exercise after 16 days of simulated microgravity was associated with greater circulating levels of NE, vasoconstriction, Q, baroreflex sensitivity, and PV.

NASA Discipline Cardiopulmonary↗
NASA NTRS1993

Cytoplasmic pH influences cytoplasmic calcium in MC3T3-E1 osteoblast cells

We found that the cytoplasmic concentration of calcium (Cai) of MC3T3-E1 osteoblasts was influenced by the type of pH buffer we used in the perfusing medium, suggesting that intracellular pH (pHi) might influence Cai. To study this effect, the Cai and pHi were monitored as we applied various experimental conditions known to change pHi. Exposure to NH4Cl caused a transient increase in both pHi and Cai without a change in extracellular pH (pHo). Decreasing pHo and pHi by lowering the bicarbonate concentration of the medium decreased Cai, and increasing pHi by the removal of 5% CO2 increased Cai. Clamping pHi to known values with 10 microM nigericin, a potassium proton ionophore, also influenced Cai: acid pHi lowered Cai, whereas alkaline pHi increased it. The rise in Cai appears to be very sensitive to the extracellular concentration of calcium, suggesting the existence of a pH-sensitive calcium influx mechanism. We conclude that physiologic changes in pH could modulate Cai by controlling the influx of calcium ions and could change the time course of the Cai transient associated with hormonal activation.

NASA Program Space Biology↗
NASA NTRS1995

Motor adaptation to Coriolis force perturbations of reaching movements: endpoint but not trajectory adaptation transfers to the nonexposed arm

1. Reaching movements made in a rotating room generate Coriolis forces that are directly proportional to the cross product of the room's angular velocity and the arm's linear velocity. Such Coriolis forces are inertial forces not involving mechanical contact with the arm. 2. We measured the trajectories of arm movements made in darkness to a visual target that was extinguished at the onset of each reach. Prerotation subjects pointed with both the right and left arms in alternating sets of eight movements. During rotation at 10 rpm, the subjects reached only with the right arm. Postrotation, the subjects pointed with the left and right arms, starting with the left, in alternating sets of eight movements. 3. The initial perrotary reaching movements of the right arm were highly deviated both in movement path and endpoint relative to the prerotation reaches of the right arm. With additional movements, subjects rapidly regained straight movement paths and accurate endpoints despite the absence of visual or tactile feedback about reaching accuracy. The initial postrotation reaches of the left arm followed straight paths to the wrong endpoint. The initial postrotation reaches of the right arm had paths with mirror image curvature to the initial perrotation reaches of the right arm but went to the correct endpoint. 4. These observations are inconsistent with current equilibrium point models of movement control. Such theories predict accurate reaches under our experimental conditions. Our observations further show independent implementation of movement and posture, as evidenced by transfer of endpoint adaptation to the nonexposed arm without transfer of path adaptation. Endpoint control may occur at a relatively central stage that represents general constraints such as gravitoinertial force background or egocentric direction relative to both arms, and control of path may occur at a more peripheral stage that represents moments of inertia and muscle dynamics unique to each limb. 5. Endpoint and path adaptation occur despite the absence both of mechanical contact cues about the perturbing force and visual or tactile cues about movement accuracy. These findings point to the importance of muscle spindle signals, monitoring of motor commands, and possibly joint and tendon receptors in a detailed trajectory monitoring process. Muscle spindle primary and secondary afferent signals may differentially influence adaptation of movement shape and endpoint, respectively.

Non-NASA Center↗
NASA NTRS1995

Geometric adjustments to account for eye eccentricity in processing horizontal and vertical eye and head movement data

Neglecting the eccentric position of the eyes in the head can lead to erroneous interpretation of ocular motor data, particularly for near targets. We discuss the geometric effects that eye eccentricity has on the processing of target-directed eye and head movement data, and we highlight two approaches to processing and interpreting such data. The first approach involves determining the true position of the target with respect to the location of the eyes in space for evaluating the efficacy of gaze, and it allows calculation of retinal error directly from measured eye, head, and target data. The second approach effectively eliminates eye eccentricity effects by adjusting measured eye movement data to yield equivalent responses relative to a specified reference location (such as the center of head rotation). This latter technique can be used to standardize measured eye movement signals, enabling waveforms collected under different experimental conditions to be directly compared, both with the measured target signals and with each other. Mathematical relationships describing these approaches are presented for horizontal and vertical rotations, for both tangential and circumferential display screens, and efforts are made to describe the sensitivity of parameter variations on the calculated results.

NASA Discipline Neuroscience↗
NASA NTRS1989

Psychology of computer use: IX. A menu of self-administered microcomputer-based neurotoxicology tests

This study examined the feasibility of repeated self-administration of a newly developed battery of mental acuity tests which may have application in screening for fitness-for-duty or for persons who may be exposed to environmental stress, toxic agents, or disease. 16 subjects self-administered 18 microcomputer-based tests (13 new, 5 "core"), without proctors, over 10 sessions. The hardware performed well throughout the study and the tests appeared to be easily self-administered. Stabilities and reliabilities of the tests from the "core" battery were comparable to those obtained previously under more controlled experimental conditions. Eight of the new tests exceeded minimum criteria for metric and practical requirements and can be recommended as additions to the menu. Although the average retest reliability was high, cross-correlations between tests were low, implying factorial diversity. The menu can be used to form batteries with flexible total testing time which are likely to tap different mental processes and functions.

NASA Discipline Neuroscience↗
NASA NTRS2005

Full-Field Measurements of Self-Excited Oscillations in Momentum-Dominated Helium Jets

Flow structure of momentum-dominated helium jets discharged vertically into ambient air was investigated using a high-speed rainbow schlieren deflectometry (RSD) apparatus operated at up to 2000 Hz. The operating parameters, i.e., Reynolds number and Richardson number were varied independently to examine the self-excited, flow oscillatory behavior over a range of experimental conditions. Measurements revealed highly periodic oscillations in the laminar region at a unique frequency as well as high regularity in the flow transition and initial turbulent regions. The buoyancy was shown to affect the oscillation frequency and the distance from the jet exit to the flow transition plane. Instantaneous helium concentration contours across the field of view revealed changes in the jet flow structure and the evolution of the vortical structures during an oscillation cycle. A cross-correlation technique was applied to track the vortices and to find their convection velocity. Time-traces of helium concentration at different axial locations provided detailed information about the oscillating flow.

Yildirim, B. S.↗
NASA NTRS2004

Concentration Measurements in Self-Excited, Momentum-Dominated Helium Jets

Flow structure of momentum-dominated pure helium jets discharged vertically into ambient air was investigated using high-speed rainbow schlieren deflectometry (RSD) technique. Effects of the operating parameters, i.e., Reynolds number (Re) and Richardson number (Ri), on the oscillatory behavior of the flow were examined over a range of experimental conditions. To seek the individual effect of these parameters, one of them was fixed and the other was varied with certain constraints. Measurements revealed highly periodic oscillations in the laminar region as well as high regularity in transition and turbulent regions. Maximum spectral power profiles at different axial locations indicated the oscillation amplitude increasing until the breakdown of the jet in the turbulent regime. The transition from the laminar to turbulent flow was also investigated. Fast Fourier transform analysis performed in the transition regime showed that the flow oscillates at a unique frequency, which was the same in the upstream laminar flow region. Measured deflection angle data were used in Abel inversion algorithm to construct the helium concentration fields. Instantaneous helium concentration contours revealed changes in the flow structure and evolution of vortical structures during an oscillation cycle. Temporal evolution plots of helium concentration at different axial location showed repeatable oscillations at all axial and radial locations up to the turbulent regime. A cross-correlation technique, applied to find the spatial displacements of the vortical structures, provided correlation coefficient peaks between consecutive schlieren images. Results show that the vortical structure convected and accelerated only in the axial direction.

Yildirim, Bekir Sedat↗
NASA NTRS2005

Sulfur Oxidation and Contrail Precursor Chemistry

Sulfuric acid (H2SO4), formed in commercial aircraft operations via Fuel-S (right arrow) SO2 + SO3 (right arrow) H2SO4, plays an important role in affecting the global climate change through atmospheric chemical reactions and radiative forcing. Measurement of the sulfur oxidation rates is critical to the understanding of the contrail formation. The principle reaction pathway is SO2 + O + M (right arrow) SO3 + M. Although there are many measurements for the rates of this reaction, it has never been measured in the temperature and pressure regime available to aircraft operation. In this investigation, a series of experiments were performed behind the reflected shock waves in a shock tube. OH radicals were produced in lean, shock heated SO2/H2/O2/Ar mixtures. The reaction progress was followed using OH absorption spectroscopy at 310 nm. The data were analyzed with the aid of computer modeling/simulation. The mean value of the rate coefficients of R21 determined is k(sub 21,0)/[M]= 3.9 x 10(exp 15) cm(sup 6) per square mole per second at T = 960 - 1150 K and rho = 16-30 micromole per cubic centimeter with uncertainty limits of plus or minus 30%. A non-Arrhenius fit to our data together with all existing data gives k(sub 21,0)/[M] = 1.3 x 10(exp 24) T (exp -2.5) exp(-2350 K/T) cm(sup 6) per square mole per second at T = 300 - 2500 K with the same uncertainty limits given above. The calculated conversion of S(IV)(SO2) to S(VI) (SO3 + H2SO4) was about 2% in our experimental conditions.

DeWitt, Kenneth↗
NASA NTRS2001

Diffusivity Measurements Made Instant and Easy

A compact common path interferometer (CPI) system has been developed to measure the diffusivity of liquid pairs. The CPI is an optical technique that can be used to measure changes in the gradient of the refraction index of transparent materials. It uses a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. The molecular diffusion coefficient of liquids can be determined from the physical relations between changes in the optical path length and liquid phase properties. When the data obtained by using the CPI have been compared with similar results from other techniques, the instrument has been demonstrated to be far superior to other instruments for measuring the diffusivity of miscible liquids while staying very compact and robust (ref. 1). Because of its compactness and ease of use, the CPI has been adopted for use in studies of interface dynamics as well as other diffusion-controlled process applications (ref. 2). This progress will permit experiments in microgravity that can quantitatively answer basic science questions about mass and thermal diffusion and their effect in transport processes. This instrument is a spinoff of a diagnostic development for microgravity fluid physics experiments at the NASA Glenn Research Center that has used optics and electronics existing in the fluid physics laboratory for feasibility studies. Optical diagnostic techniques have become an integral part of many areas of measurement applications in industrial and research laboratories. Many types of interferometers and their phase-shifted versions have been used as instruments for measuring optical wave fronts for lens testing and combustion and fluid flow diagnostics. One of these, the point diffraction interferometer, is considered to be robust (see, for example, ref. 3) because it has a common-path design. The point diffraction interferometer is difficult to align and has a limited measurement range for liquid-phase applications. Interferometry and schlieren techniques have been widely used for many years for gas-flow-visualization. On the other hand, the CPI, which is basically a Wollaston prism Polarizer in combination with an analyser (crystalline quartz retardation plate) is used instead of a point diffraction interferometer unit. The advantage of using the CPI over other optical techniques is that it can make quantitative measurements in liquids with the large index of refraction variations that often occur in interface dynamics studies. This can be simply accomplished by using different prism polarizers for each particular experimental condition.

Rashidnia, Nasser↗
NASA NTRS2004

Magnetohydrodynamic and Paramagnetic Phenomena in Electrochemistry with Diamagnetic and Ferromagnetic Millielectrodes

There are three kinds of body forces operating in electrolytic solutions in the magnetic field: the magnetohydrodynamic force F(sub B) (=i x B), the F(sub delB) force (approximately B(raised dot)gradB) and the F(sub delC) force (approximately |B|(sup 2)gradC). These three forces manifest themselves differently, depending on the experimental conditions. Thus, diamagnetic disc millielectrodes (e.g., Au) with their plane parallel to the flux density of the homogeneous magnetic field of an electromagnet yield convective behavior analogous to that observed with rotating electrodes; that response is controlled by F(sub B). The same electrodes placed in the inhomogeneous field of a strong permanent magnet yield also convective behavior that is controlled by both F(sub B) and F(sub delB). Finally, similarly sized millielectrodes made of permanent magnets (e.g., Au-coated Nd-Fe-B discs) yield diffusion-controlled behavior at conditions where a gold disc electrode shows behavior dominated by density gradient driven natural convection; in this case the predominant forces are both F(sub delB) and F(sub delC). Under open circuit conditions, ferromagnetic (i.e., magnetizable) millielectrodes (Co, Fe, Ni) dipped in corrosive solutions and placed in homogeneous magnetic fields yield mass-transfer phenomena that seem to be controlled by magnetophoresis.

Leventis, Nicholas↗
NASA NTRS2005

The Influence of Roughness on Gear Surface Fatigue

Gear working surfaces are subjected to repeated rolling and sliding contacts, and often designs require loads sufficient to cause eventual fatigue of the surface. This research provides experimental data and analytical tools to further the understanding of the causal relationship of gear surface roughness to surface fatigue. The research included evaluations and developments of statistical tools for gear fatigue data, experimental evaluation of the surface fatigue lives of superfinished gears with a near-mirror quality, and evaluations of the experiments by analytical methods and surface inspections. Alternative statistical methods were evaluated using Monte Carlo studies leading to a final recommendation to describe gear fatigue data using a Weibull distribution, maximum likelihood estimates of shape and scale parameters, and a presumed zero-valued location parameter. A new method was developed for comparing two datasets by extending the current methods of likelihood-ratio based statistics. The surface fatigue lives of superfinished gears were evaluated by carefully controlled experiments, and it is shown conclusively that superfinishing of gears can provide for significantly greater lives relative to ground gears. The measured life improvement was approximately a factor of five. To assist with application of this finding to products, the experimental condition was evaluated. The fatigue life results were expressed in terms of specific film thickness and shown to be consistent with bearing data. Elastohydrodynamic and stress analyses were completed to relate the stress condition to fatigue. Smooth-surface models do not adequately explain the improved fatigue lives. Based on analyses using a rough surface model, it is concluded that the improved fatigue lives of superfinished gears is due to a reduced rate of near-surface micropitting fatigue processes, not due to any reduced rate of spalling (sub-surface) fatigue processes. To complete the evaluations, surface inspection were completed. The surface topographies of the ground gears changed substantially due to running, but the topographies of the superfinished gears were essentially unchanged with running.

Krantz, Timothy↗
NASA NTRS2004

Does Magnetic Field Affect Malaria Parasite Replication in Human Red Blood Cells?

Digestion of red blood cell (RBC) hemoglobin by the malaria parasite results in the formation of paramagnetic hemazoin crystals inside the parasite body. A number of reports suggest that magnetic field interaction with hamazoin crystals significantly reduces the number of infected cells in culture, and thus magnetic field can be used to combat malaria. We studies the effects of magnetic filed on the Plasmodium falciparum asexual life cycle inside RBCs under various experimental conditions. No effect was found during prolonged exposure of infected RBCs to constant magnetic fields up to 6000 Gauss. Infected RBCs were also exposed, under temperature-controlled conditions, to oscillating magnetic fields with frequencies in the range of 500-20000 kHz, and field strength 30-600 Gauss. This exposure often changed the proportion of different parasite stages in treated culture compared to controls. However, no significant effect on parasitemia was observed in treated cultures. This result indicates that the magnetic field effect on Plasmodium falciparum is negligible, or that hypothetical negative and positive effects on different stages within one 48-hour compensate each other.

Chanturiya, Alexandr N.↗
NASA NTRS2002

Molecular modeling of interactions in electronic nose sensors for environmental monitoring

We report a study aimed at understanding analyte interactions with sensors made from polymer-carbon black composite films. The sensors are used in an Electronic Nose (ENose) which is used for monitoring the breathing air quality in human habitats. The model mimics the experimental conditions of the composite film deposition and formation and was developed using molecular modeling and simulation tools. The Dreiding 2.21 Force Field was used for the polymer and analyte molecules while graphite parameters were assigned to the carbon black atoms. The polymer considered for this work is methyl vinyl ether / maleic acid copolymer. The target analytes include both inorganic (NH3) and organic (methanol) types of compound. Results indicate different composite-analyte interaction behavior.

electronic noise polymer-carbon composite molecula↗
NASA NTRS1994

The Production of NO subscript 2 from the Photolysis of Peroxyacetyl Nitrate

PAN vapor was photolyzed at 248 nm and the NO subscript 2 photoproduct was detected by laser induced fluorescence (LIF). By comparison to the NO subscript 2 production from the photolysis of HNO subscript 3 under identical experimental conditions, we have obtained a relative quantum yield for the production of NO subscript 2. The implications of these results for atmospheric PAN chemistry will be discussed.

Peroxyacetyl nitrate fluorescence↗
NASA NTRS2005

The electron excited ultraviolet spectrum of HD : cross sections and transition probabilities

We have analyzed the high-resolution ultraviolet (UV) emission spectrum of molecular deuterium hydride (HD) excited by electron impact at 100 eV under optically thin, single-scattering experimental conditions. The high-resolution spectrum (FWHM=160 mA) spans the wavelength range from 900 to 1650 A and contains the two Rydberg series of HD: (sup 1)Sigma(sub u)(sup +)1s(sigma), np(si n=2, 3, 4) --> X(sup 1)Sigma(sub g)(sup +) and (sup 1)Pi(sub u)(sup +)1s(sigma), np(pi)(C,D,D',D'', n=2, 3, 4, 5) -->X(sup 1)Sigma(sub g)(sup +). A model spectrum of HD, based on newly calculated tra rovibrational coupling for the strongest band systems, B (sup 1)Sigma(sub u)(sup +)-X(sup 1)Sigma(sub g)(sup +),B'(sup 1)Sigma(sub g)(sup +)-X(sup 1)Sigma(sub g)(sup +),C(sup 1)Pi(sub u)-X(sup 1)Sigm sections for direct excitation at 100 eV of the B (sup 1)Sigma(sub u)(sup +), B' (sup 1)Sigma(sub u)(sup +), C(sup 1)Pi(sub u), and D(sup 1)Pi(sub u) states were derived from a model analysis of the state. The absolute cross section values for excitation to the B (sup 1)Sigma(sub u)(sup +), B' (sup 1)Sigma(sub u)(sup +), C(sup 1)Pi(sub u), and D(sup 1)Pi(sub u) states were found to be (2.57+/-0. and (0.17+/-0.04)x10(exp -17) sq cm, respectively. We have also determined the dissociative excitation cross sections at 100 eV for the emission of Ly(alpha) at 1216 A and Ly(Beta) at 1025 A lines, which are (7.98+/-1.12)x10(exp -18) and (0.40+/-0.10)x10(exp -18) sq cm, respectively. The summed excitation function of the closely spaced pair of lines, H Ly(alpha) and D Ly(Beta), resulting from excitation of HD, has been measured from the threshold to 800 eV and is analytically modeled with a semiempirical relation. The model cross sections are in good agreement with the corrected Ly(alpha) cross sections of Mohlmann et al. up to 2 keV. Based on measurements of H, D (2s) production cross section values by Mohlmann et al., the H, D (n=2) cross section is estimated to be 1.6 x 10(exp -17) sq cm at 100 eV.

molecular data↗