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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Study of the extra-ionic electron distributions in semi-metallic structures by nuclear quadrupole resonance techniques

A straightforward self-consistent method was developed to estimate solid state electrostatic potentials, fields and field gradients in ionic solids. The method is a direct practical application of basic electrostatics to solid state and also helps in the understanding of the principles of crystal structure. The necessary mathematical equations, derived from first principles, were presented and the systematic computational procedure developed to arrive at the solid state electrostatic field gradients values was given.

Murty, A. N.↗
NASA NTRS1975

Density-dependent frequency shift of the hydrogen S2/1/ quadrupole line

An optical parametric oscillator pumped with an Nd:YAG laser was used in the investigations along with a White cell and a scanning spectrometer. The frequency of the S2(1) line was measured at a temperature of about 293 K over the density range from 1 to 4.3 amagat with the aid of a technique reported by Douglas and Sharma (1953). It was found that the obtained data are in good agreement with measurements conducted by Fink et al. (1965).

Chackerian, C., Jr.↗
NASA NTRS1980

Strouhal number influence on flight effects on jet noise radiated from convecting quadrupoles

The paper reports a complementary extension of previous work to include the high-frequency features reflected in the discussion of the higher Strouhal number influence on flight effects. It is found that, in addition to the usual features of flight effects on noise from ordinary flows, the high Strouhal number flows exhibit some more interesting features which are uniquely characteristic to them. The additional features are as follows: (1) Flight effects are more favorable to hot jets than to cold jets; (2) the higher the Strouhal number of the jet flow, the lesser the forward arc amplification due to flight; (3) as the Strouhal number increases, the peak amplification angle in the forward quadrant and the peak suppression angle in the aft quadrant move toward 90 deg and get closer, thus reducing the amplification exposure to a constricted angular region; (4) the silence zone is disturbed and displaced from its normal position parallel to the jet flow to give rise to multiple crossings of flight curves with the static line; and (5) the occurrence of multiple crossings is a strange phenomenon solely characteristic of high Strouhal number with high subcritical jet flows in flight.

Dash, R.↗
NASA NTRS1989

The H2 4-0 S(0, 1, and 2) quadrupole features in Jupiter

In the wake of the detection of Jupiter's H2 S4(2) feature, low-temperature laboratory measurements of NH3 are used in a detailed analysis to ascertain an improved equivalent width for the H2 S4(0) line. Good agreement is obtained between equivalent widths computed from published models and the equivalent widths observed for this line. It is noted that the approximately 150 K effective formation line temperature at Jupiter's averaged disk center, which has been determined from the nominal S4(2)/S4(0) ratio, is in keeping with an H2 ortho-para ratio for Jovian equilibrium tropospheric H2.

Smith, Wm. Hayden↗
NASA NTRS1990

Can shock waves on helicopter rotors generate noise? - A study of the quadrupole source

An analysis has previously established that local shock surfaces attached to helicopter rotor blades moving at high subsonic speeds are potent noise generators; in pursuit of this insight, a novel formulation is presented for the prediction of the noise of a deformable shock, whose area changes as a function of the azimuthal position of the blade. The derivation of this formulation has its basis in a mapping of the moving shock to a time-independent region. In virtue of this mapping, the implementation of the main result on a computer becomes straightforward enough for incorporation into the available rotor-noise prediction code. A problem illustrating the importance of rotor shocks in the generation of high-intensity noise is presented.

Farassat, F.↗
NASA NTRS1991

Analytic potential in a linear radio-frequency quadrupole trap with cylindrical electrodes

An analytical expression is derived for a radio-frequency ion trap of novel configuration consisting of a four-sectored hollow cylinder enclosed between two end caps. The cylindrical geometry of the sectored trap provides shielding against the buildup of charge and also makes it possible to calculate the potential within the trap by solving Laplace's equation for given boundary conditions. Equations are presented for calculating the time-averaged potential generated by the RF fields, the end-cap potential, and the potential arising from the application of a dc bias on two of the four electrode sectors. It is shown that, near the ends of this trap, the effective potential arising from the RF fields acts to propel ions out of the trap and that the addition of a dc bias on two neighboring sectors generates an inhomogeneous field in the trap which produces a force on the ions along the trap's long axis in a direction dependent on the sign of the bias.

Melbourne, R. K.↗
NASA NTRS1994

Dynamics Of Ions In A Radio-Frequency Quadrupole Trap

Report describes computer-simulation study of motions of various numbers of ions in Paul trap. Study part of continuing effort to understand motions of trapped charged particles (atoms, ions, molecules, or dust particles). Motions characterized in terms of heating by radio-frequency fields, formation of crystallike structures in cold clouds of trapped particles, and other phenomena important in operation of radio-frequency traps in frequency standards.

Prestage, John D.↗
NASA NTRS1994

Line strength and self-broadening coefficient of the pure rotational S(1) quadrupole line in H2

The absolute intensity, S(sub 1), and self-broadening coefficient, gamma(sub L), for H2 S(sub zero)(1) pure rotational line at 17.0348 micrometers (587.032 cm(exp -1)) have been measured for the first time using a tunable diode laser spectrometer with a resolution of approximately 1 x 10(exp -3) cm(exp -1). By fitting a Galatry line shape convolved with a 1 x 10(exp -3) cm(exp -1) Gaussian instrument profile to absorption profiles, for H2 pressures ranging from 0.34 to 1.30 atm, values of s(sub 1) = (7.0 +/- 0.4) x 10(exp -8) cm(exp -2) atm(exp -1) and gamma(sub L) = (1.73 +/- 0.12) x 10(exp -3) cm(exp -1) atm(exp -1) were obtained.

Reuter, Dennis C.↗
NASA NTRS1995

The abundances of methane and ortho/para hydrogen on Uranus and Neptune: Implications of New Laboratory 4-0 H2 quadrupole line parameters

The tropospheric methane molar fraction (f(sub CH4, t) and the ortho/para hydrogen ratio are derived for Uranus and Neptune based on new determinations of spectroscopic parameters for key hydrogen features as reported by D. W./ Ferguson et al. (1993). For each planet, the relatively weak laboratory linestrengths (approximately 30 and 15% less than the theoretical 4-0 S(0) and S(1) linestrengths, respectively) results, when compared to analyses adopting theroetical values, in a approximately 30% decrease in the tropospheric methane ratio and a comparable increase in the pressure level of the optically thick cloudtop marking the bottom of the visible atmosphere (P(sub c/d)). The increase in the ratio of S(1)/S(0) linestrengths from 4.4 (theoretical) to approximately 5.9 (measured) results in a decrease in the range of viable ortho/para ratios; an equilibrium hydrogen distribution is now the best fit for both planets. The methane mixing ratios reported here are in agreement with the value of 0.023 derived by the Voyager Radio Occultation Experiment (G. F. Lindal, 1992) for Neptune, but slightly lower than the Voyager Uranus measurement of 0.023 reported by G. F. LIndel et al. (1987). The relative carbon-to-hydrogen abundances for Uranus and Neptune support planetary formation mechanisms involving the dissolution of carbon-bearing planetesimals in the atmospheres of both planets during their early stages of formation (e.g., J. B. Pollack et al., 1986).

Baines, Kevin H.↗