Search NASA⌕ Search

SEARCH · Search NASA

Results for “atomic electric dipole moment”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

17 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Microgravity Electron Electric Dipole Moment Experiment with a Cold Atom Beam

New physics beyond the Standard Model: The small CP violation contained in the Standard Model is insufficient to account for the baryon/antibaryon asymmetry in the universe. New sources of CP violation are provided by extensions to the Standard Model. They contain CP-violating phases that couple directly to leptons and from which a large electron electric dipole moment (EDM) may be generated. Observation of an electron EDM would be proof of a Standard Model extension because the Standard Model only allows an electron EDM of less than 10(exppp -57) C-m (S.I. units; 1 C-m = 1.6 x 10(exp -21) e-cm). A null result, however, constrains models and improving the limit tightens constraints, further restricting the models.

Gould, Harvey↗
NASA NTRS1970

Long-range interatomic dipoles

Interatomic electric dipole moment coefficient derivation by approximation involving accessible atomic properties, noting application to H atoms

Brown, W. B.↗
NASA NTRS1986

Theoretical Electric Dipole Moments of SiH, GeH and SnH

Accurate theoretical dipole moments (mu(sub c) have been computed for the X(exp 2)Pi ground states of Si(-)H(+)(0.118 D), Ge(+)H(-)(0.085 D) and Sn(+)H(-)(0.357 D). The trend down the periodic table is regular and follows that expected from the electronegativities of the group IV atoms. The dipole moment of 1.24 +/- 0.1 D for GeH recently derived by Brown, Evenson and Sears from the relative intensities of electric and magnetic dipole transitions in the 10 microns spectrum of the X(exp 2)Pi state is seriously questioned.

Pettersson, Lars G. M.↗
NASA NTRS1986

Theoretical electric dipole moments of SiH, GeH and SnH

Accurate theoretical dipole moments have been computed for the X2Pi ground states of Si(-)H(+) (0.118 D), Ge(+)H(-) (0.085 D), and Sn(+)H(-) (0.357 D). The trend down the periodic table is regular and follows that expected from the electronegativities of the group IV atoms. The dipole moment of 1.24 + or - 0.1 D for GeH recently derived by Brown, Evenson and Sears (1985) from the relative intensities of electric and magnetic dipole transitions in the 10-micron spectrum of the X2Pi state is seriously questioned.

Pettersson, L. G. M.↗
NASA NTRS2012

Primary Volatile Abundances in Comets from Infrared Spectroscopy: Implications for Reactions on Grain Surfaces in the Interstellar/Nebular Environment

Comets retain relatively primitive icy material remaining from the epoch of Solar System formation, however the extent to which they are modified from their initial state remains a key question in cometary science. High-resolution lR spectroscopy has emerged as a powerful tool for measuring vibrational emissions from primary volatiles (i.e., those contained in the nuclei of comets). With modern instrumentation, most notably NIRSPEC at the Keck II 10-m telescope, we can quantify species of astrobiological importance (e.g., H20, C2H2, CH4, C2H6, CO, H2CO, CH30H, HCN, NH3). In space environments, compounds of keen interest to astrobiology could originate from HCN and NH3 (leading to amino acids), H2CO (leading to sugars), or C2H6 and CH4 (suggested precursors of ethyl- and methylamine). Measuring the abundances of these precursor molecules (and their variability among comets) is a feasible task that contributes to understanding their delivery to Earth's early biosphere and to the synthesis of more complex pre biotic compounds. Over 20 comets have now been measured with IR spectroscopy, and this sample reveals significant diversity in primary volatile compositions. From this, a taxonomic classification scheme is emerging, presumably reflecting the diverse conditions experienced by pre-cometary grains in interstellar and subsequent nebular environs. The importance of H-atom addition to C2H2 on the surfaces of interstellar grains to produce C2H6 was validated by the discovery of abundant ethane in comet C/1996 B2 (Hyakutake) with C2H6/CH4 well above that achievable by gas-phase chemistry , and then in irradiation experiments on laboratory ices at 10 - 50 K. The large abundance ratios C2H6/CH4 observed universally in comets establish H-atom addition as an important and likely ubiquitous process, and comparing C2H6/C2H2 among comets can provide information on its efficiency. The IR is uniquely capable since symmetric hydrocarbons (e.g., C2H2, CH4, C2H6) have no electric dipole moment and thus no allowed pure rotational transitions. CO should also be hydrogenated on grain surfaces. Irradiation experiments on interstellar ice analogs show this to require very low temperatures, the resulting yields of H2CO and CH30H being highly dependent on temperature in the range approx 10 - 25 K. The relative abundances of these chemically-related molecules in comets provide one measure of the efficiency of H-atom addition to CO Oxidation of CO is also important on grain mantles, as evidenced by the widespread presence of C02 ice towards interstellar sources observed with ISO and in a survey of 17 comets observed with AKARI. H-atom addition to C2H2 produces the vinyl radical, and through subsequent oxidation1reduction reactions can lead to vinyl alcohol, acetaldehyde, and ethanol This may have implications for interpreting observed abundance ratios CO/C2H2. We will discuss possible implications regarding formation conditions in the context of measured primary volatile compositions, emphasizing recently observed comets and published results. These are continually providing new insights regarding our taxonomic scheme and also delivery of pre-biological material to the young Earth.

DiSanti, M. A.↗
NASA NTRS1992

Equilibrium properties of transition-metal ion-argon clusters via simulated annealing

The geometrical structures of M(+) (Ar)n ions, with n = 1-14, have been studied by the minimization of a many-body potential surface with a simulated annealing procedure. The minimization method is justified for finite systems through the use of an information theory approach. It is carried out for eight potential-energy surfaces constructed with two- and three-body terms parametrized from experimental data and ab initio results. The potentials should be representative of clusters of argon atoms with first-row transition-metal monocations of varying size. The calculated geometries for M(+) = Co(+) and V(+) possess radial shells with small (ca. 4-8) first-shell coordination number. The inclusion of an ion-induced-dipole-ion-induced-dipole interaction between argon atoms raises the energy and generally lowers the symmetry of the cluster by promoting incomplete shell closure. Rotational constants as well as electric dipole and quadrupole moments are quoted for the Co(+) (Ar)n and V(+) (Ar)n predicted structures.

Asher, Robert L.↗
NASA NTRS1973

Calculated dipole moment and energy in collision of a hydrogen molecule and a hydrogen atom

Calculations were carried out using three Slater-type 1s orbitals in the orthogonalized valencebond theory of McWeeny. Each orbital exponent was optimized, the H2 internuclear distance was varied from 7.416 x 10 to the -11th power to 7.673 x 10 to the -11th power m (1.401 to 1.450 bohrs). The intermolecular distance was varied from 1 to 4 bohrs (0.5292 to 2.117 x 10 to the 10th power). Linear, scalene, and isosceles configurations were used. A weighted average of the interaction energies was taken for each intermolecular distance. Although energies are tabulated, the principal purpose was to calculate the electric dipole moment and its derivative with respect to H2 internuclear distance.

Patch, R. W.↗
NASA NTRS1980

Electron-impact excitation of the singlet states of N2. I - The Birge-Hopfield system /b 1 pi u - X 1 Sigma g +/

Results of a study of the electron-impact excitation of the b 1 pi u state of N2, one of the singlet states thought to be excited by precipitating electrons in the auroral zones, and of its predissociation and radiative relaxation through the emission of the Birge-Hopfield band system (b 1 pi u - X 1 Sigma g +) are presented. A collimated electron beam was passed through N2 gas producing a variety of atomic states through dissociative excitation, and the radiation resulting from relaxation of these states was observed by VUV and visible-IR monochromators. Absolute emission cross sections for 11 Birge-Hopfield bands are obtained for energies from threshold to 500 eV, and used to calculate the absolute transition probabilities for BH(1, v-prime) bands and the variation of the electric dipole moment with internuclear distance. With the exception of the v-prime equals 1, 5 and 6 vibrational levels, all b 1 pi u levels are found to predissociate with a specific predissociation branching ratio greater than 0.99, representing a major source of nitrogen atoms.

Zipf, E. C.↗
NASA NTRS1984

The far-infrared laser magnetic resonance spectrum of the SiH radical and determination of ground state parameters

The far-infrared laser magnetic resonance spectrum of the SiH radical in the v = O level of its X2Pi state has been recorded. The signals are rather weak. The molecules were generated in the reaction between fluorine atoms and SiH4. Rotational transitions have been detected in both 2Pi1/2 and 2Pi3/2 spin components but no fine structure transitions between the spin components were observed. Proton hyperfine splittings were resolved on some lines. The measurements have been analyzed, subjected to a least-squares fit using an effective Hamiltonian, and the appropriate molecular parameters determined. The weakness of the spectrum and the failure of attempts to power saturate favorable lines are both consistent with a small value for the electric dipole moment for SiH.

Brown, J. M.↗
NASA NTRS2003

New Experiment to Measure the Electron Electric Dipole Moment

An electron can possess an electric dipole moment (edm) only if time reversal symmetry (T) is violated. No edm of any particle has yet been discovered. CP-violation, equivalent to T-violation by the CPT theorem, does occur in Kaon decays and can be accounted for by the standard model. However, this mechanism leads to an electron edm d(sub e) of the order of 10(exp -38) e cm, whereas the current experimental bound on d(sub e) is about 10(exp -27) e cm. However, well-motivated extensions of the standard model such as supersymmetric theories do predict that de could be as large as the current bound. In addition, CP violation in the early universe is required to explain the preponderance of matter over anti-matter, but the exact mechanism of this CP violation is unclear. For these reasons, we are undertaking a new experimental program to determine de to an improved accuracy of 10(exp -29) e cm. Our experiment will use laser-cooled, trapped Cesium atoms to measure the atomic edm d(sub Cs) that occurs if d(sub e) is not zero. In order to do this, we will measure the energy splitting between the atoms spin states in parallel electric and magnetic fields. The signature of an edm would be a linear dependence of the splitting on the electric field E due to the interaction - d(sub Cs) dot E. Our measurement will be much more sensitive than previous measurements because atoms can be stored in the trap for tens of seconds, allowing for much narrower Zeeman resonance linewidths. Also, our method eliminates the most important systematic errors, proportional to atomic velocity, which have limited previous experiments. In this presentation, we will describe the design of our new apparatus, which is presently under construction. An important feature of our experimental apparatus is that magnetic field noise will be suppressed to a very low value of the order of 1 fT/(Hz)1/2. This requires careful attention to the Johnson noise currents in the chamber, which have not been important in previous experiments. In addition we will present estimates of the limits of the various errors that we expect for our experiment.

Kittle, Melanie↗
NASA NTRS1985

Theoretical transition probabilities between the lowest 2S, 2P and 2D states of Na, K, Rb and Cs

Theoretical transition probabilities between the lowest 2S, 2P and 2D states of the alkali atoms Na through Cs have been computed using near Hartree-Fock quality Slater basis sets. The important core-valence correlation effects are incorporated explicitly by a configuration-interaction procedure. For Cs, the calculations were repeated using a Gaussian basis set so that relativistic effects could be incorporated through an effective core potential procedure. The best calculated electric quadrupole Einstein coefficients are Na(196.3/s), K(103.6/s), Rb(72.4/s) and Cs(19.7/s). Core-valence effects become increasingly important down the column, and reduce the quadrupole transition strengths to about the same degree as for the 2P-2S and 2D-2P dipole-allowed transitions. Relativistic effects increase the quadrupole moment of Cs, but less so than in Ba, presumably because the alkali 2D states are more diffuse.

Langhoff, S. R.↗
NASA NTRS1985

Infrared and far-infrared laser magnetic resonance spectroscopy of the GeH radical - Determination of ground state parameters

The GeH radical has been detected in its ground 2 Pi state in the gas phase reaction of fluorine atoms with GeH4 by laser magnetic resonance techniques. Rotational transitions within both 2 Pi 1/2 and 2 Pi 3/2 manifolds have been observed at far-infrared wavelengths and rotational transitions between the two fine structure components have been detected at infrared wavelengths (10 microns). Signals have been observed for all five naturally occurring isotopes of germanium. Nuclear hyperfine structure for H-1 and Ge-73 has also been observed. The data for the dominant isotope (/Ge-74/H) have been fitted to within experimental error by an effective Hamiltonian to give a set of molecular parameters for the X 2 Pi state which is very nearly complete. In addition, the dipole moment of GeH in its ground state has been estimated from the relative intensities of electric and magnetic dipole transitions in the 10 micron spectrum to be 1.24(+ or - 0.10) D.

Brown, J. M.↗
NASA NTRS1994

Molecular Dynamics of a Water-Lipid Bilayer Interface

We present results of molecular dynamics simulations of a glycerol 1-monooleate bilayer in water. The total length of analyzed trajectories is 5ns. The calculated width of the bilayer agrees well with the experimentally measured value. The interior of the membrane is in a highly disordered fluid state. Atomic density profile, orientational and conformational distribution functions, and order parameters indicate that disorder increases toward the center of the bilayer. Analysis of out-of-plane thermal fluctuations of the bilayer surfaces occurring at the time scale of the present calculations reveals that the distribution of modes agrees with predictions of the capillary wave model. Fluctuations of both bilayer surfaces are uncorrelated, yielding Gaussian distribution of instantaneous widths of the membrane. Fluctuations of the width produce transient thinning defects in the bilayer which occasionally span almost half of the membrane. The leading mechanism of these fluctuations is the orientational and conformational motion of head groups rather than vertical motion of the whole molecules. Water considerably penetrates the head group region of the bilayer but not its hydrocarbon core. The total net excess dipole moment of the interfacial water points toward the aqueous phase, but the water polarization profile is non-monotonic. Both water and head groups significantly contribute to the surface potential across the interface. The calculated sign of the surface potential is in agreement with that from experimental measurements, but the value is markedly overestimated. The structural and electrical properties of the water-bilayer system are discussed in relation to membrane functions, in particular transport of ions and nonelectrolytes across membranes.

Wilson, Michael A.↗
NASA NTRS2003

Models And Experiments Of Laminar Diffusion Flames In Non-Uniform Magnetic Fields

Non-uniform magnetic fields affect laminar diffusion flames as a result of the paramagnetic and diamagnetic properties of the products and reactants. Paramagnetism is the weak attraction to a magnetic field a material exhibits as a result of permanent magnetic dipole moments in the atoms of the material. Diamagnetism is the weak repulsion to a magnetic field exhibited by a material due to the lack of permanent magnetic dipole moments in the atoms of a material. The forces associated with paramagnetic and diamagnetism are several orders of magnitude less than the forces associated with the more familiar ferromagnetism. A typical example of a paramagnetic gas is oxygen while hydrocarbon fuels and products of combustion are almost always diamagnetic. The fact that magnets can affect flame behavior has been recognized for more than one hundred years. Early speculation was that such behavior was due to the magnetic interaction with the ionized gases associated with a flame. Using a scaling analysis, it was later shown that for laminar diffusion flames the magnetic field/ionized gas interaction was insignificant to the paramagnetic and diamagnetic influences. In this effort, the focus has been on examining laminar diffusion slot flames in the presence of non-uniform upward decreasing magnetic fields produced using permanent magnets. The principal reason for choosing slot flames was mathematical models of such flames show an explicit dependence on gravitational body forces, in the buoyancy-controlled regime, and an applied magnetic field would also impose a body force. In addition, the behavior of such flames was more easily visualized while maintaining the symmetry of the two-dimensional problem whereas it would have been impossible to obtain a symmetric magnetic field around a circular flame and still visually record the flame height and shape along the burner axis. The motivation for choosing permanent magnets to produce the magnetic fields was the assumption that space-related technologies based on the knowledge gained during this investigation would more likely involve permanent magnets as opposed to electromagnets. While no analysis has been done here to quantify the impact that an electric field, associated with an electromagnetic, would have relative to the paramagnetic and diamagnetic interactions, by using permanent magnets this potential effect was completely eliminated and thus paramagnetic and diamagnetic effects were isolated.

Baker, J.↗