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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Accurate determination of the fine-structure intervals in the 3P ground states of C-13 and C-12 by far-infrared laser magnetic resonance

Accurate values are presented for the fine-structure intervals in the 3P ground state of neutral atomic C-12 and C-13 as obtained from laser magnetic resonance spectroscopy. The rigorous analysis of C-13 hyperfine structure, the measurement of resonant fields for C-12 transitions at several additional far-infrared laser frequencies, and the increased precision of the C-12 measurements, permit significant improvement in the evaluation of these energies relative to earlier work. These results will expedite the direct and precise measurement of these transitions in interstellar sources and should assist in the determination of the interstellar C-12/C-13 abundance ratio.

Cooksy, A. L.↗
NASA NTRS2011

A Laboratory and Theoretical Study of Silicon Hydroxide SiOH

The rotational spectrum of the triatomic free radical SiOH in its X 2A' ground electronic state has been observed in a supersonic molecular beam by Fourier transform microwave spectroscopy. The fundamental (10,1 yields 00,0) transition has been detected for normal SiOH and for three rare isotopic species: (30)SiOH, Si(18)OH, and SiOD. The same transition has also been observed in two of three excited vibrational states, v2 and v3, for the most abundant species. Precise spectroscopic constants, including those that describe the effective spin doubling and hydrogen hyperfine structure, have been derived for each isotopic species or vibrational state. To complement the laboratory work, theoretical calculations of the structure, dipole moment, and energies of the X 2A' and low-lying 1 2A'' states have also been undertaken at the coupled cluster level of theory. In agreement with theoretical predictions, we conclude from the hyperfine constants that SiOH is a best described as a pi-type radical, with the unpaired electron localized on a p orbital on the silicon atom. Assuming a bond angle of 118.5 deg, the Si-O bond length is 1.647(2) Angstroms and the O-H bond length is 0.969(4) Angstrom.

McCarthy, M. C.↗
NASA NTRS1982

Determination of the lifetime of the Mercury 6/3/P-1 state

A pulsed tunable dye laser was used for a high resolution experimental study of mercury fluorescence from the 6(3)P-1 state. The output of the dye laser was frequency doubled into the 253.7 nm region using a potassium pentaborate crystal. Exponential decays were separately observed for each of the five individual components of the hyperfine structure and the effects of the trapping of resonance radiation on the observed lifetime of the 6(3)P-1 state of mercury were investigated for each resolvable component. Within experimental error, the natural radiative lifetime of the 6(3)P-1 state was found to be independent of the hyperfine component irradiated and a value of 122 + or 2 nsec was obtained, consistent with results found by other methods.

Halstead, J. A.↗
NASA NTRS1981

Time-resolved spectroscopy of the Mercury 6 3P1 state

The time-resolved fluorescence was observed from the Hg 6 3P1 state under the influence of the earth's magnetic field and with applied fields of up to 14 G. Modulation of the fluorescence decay signal was observed as a function of both time and space and can be interpreted in terms of a classical precession of the excited atom about the magnetic field or as quantum beats resulting from interference between coherently populated Zeeman sublevels. This modulation was studied for each of the five resolvable components of the hyperfine structure separately. The fluorescence from the even isotopes was determined to be almost completely modulated while the fluorescence from the odd isotopes was only partially modulated. The frequency of modulation of the fluorescence from the mercury-202 isotope was observed as a function of the applied magnetic field and a value for the Lande factor of 1.46 + or - 0.03 was obtained. This is within experimental error of the accepted value of 1.486. In addition, the frequency of modulation as a function of applied magnetic field was determined for each of the three resolvable components with more than one contributing isotopic hyperfine line. An investigation of the effect of radiation trapping on the degree modulation was also made.

Halstead, J. A.↗
NASA NTRS1972

Laboratory measurement of the 2-centimeter, 2/11/-2/12/ transition of normal formaldehyde and its carbon-13 and oxygen-18 species.

Beam-maser spectrometric measurements to an accuracy of about 100 Hz have been conducted of the 2(11)-2(12) transition for the isotopic species of greatest astronomical interest - i.e., H2CO, H2(13)CO, and H2C(18)O. The samples used were not isotopically enriched, monomeric formaldehyde vapors. For these species, all the coupling constants required to calculate the hyperfine structure of any rotational transition have been determined.

Tucker, K. D.↗
NASA NTRS1974

Beam maser measurements of CH3OH rotational transitions

Precise measurements of rotational transitions in methanol are reported that were made by means of beam maser spectrometers. No hyperfine structure was resolved at a resonance line width of 8 kHz. Accurate center frequencies for the transitions measured are useful for determining Doppler shifts for observed interstellar lines.

Gaines, L.↗
NASA NTRS1974

Tentative identification of U93.174 as the molecular ion N2H/+/

On the basis of a consideration of the rotation constant and the hyperfine structure together with the results of an ab initio structural calculation it is suggested that the three closely space new interstellar lines near 93.174 GHz reported by Turner (1974) might have been produced by the molecular ion N2H(+). It is pointed out that the identification of N2H(+) is reasonable also in terms of current ideas of interstellar chemistry.

Green, S.↗
NASA NTRS1975

Constraints on the molecular properties of interstellar X-ogen derived from radio observations

Twenty-eight X-ogen emission sources at 89.189 GHz have been detected and observed. Twenty of these are new X-ogen sources which also contain other interstellar molecules. No infrared stars are found to be X-ogen sources. A new rest frequency (89,188.65 MHz) is derived for X-ogen. It is shown that X-ogen is not SiC, C2H, or any molecule with spin-doubling, hyperfine structure, or both.

Hollis, J. M.↗
NASA NTRS1975

Mossbauer effect in dilute iron alloys

The effects of variable concentration, x, of Aluminum, Germanium, and Lanthanum atoms in Iron lattice on various Mossbauer parameters was studied. Dilute binary alloys of (Fe-Al), (Fe-Ge), (Fe-Al) containing up to x = 2 a/o of the dilute constituent were prepared in the form of ingots and rolled to a thickness of 0.001 in. Mossbauer spectra of these targets were then studied in transmission geometry to measure changes in the hyperfine field, peak widths isomer shifts as well as the ratio of the intensities of peaks (1,6) to the intensities of peaks (2,5). It was shown that the concept of effective hyperfine structure field in very dilute alloys provides a useful means of studying the effects of progressively increasing the solute concentration on host lattice properties.

Singh, J. J.↗
NASA NTRS1977

Measurement of the fundamental vibration-rotation spectrum of ClO

The ClO fundamental absorption band near 850/cm is observed, with a tunable PbSnTe diode laser used as a source of monochromatic radiation. The chlorine monoxide concentration in the absorption tube was measured indirectly via a UV transmission technique. Frequencies and assignments for the ClO lines, and band centers and rotational constants for the ClO fundamental vibration, are tabulated. Diatomic vibration-rotation transitions within and between electronic substates are discussed. The tunable diode laser is valuable for studying the hyperfine structure. The IR spectroscopic technique is developed in order to monitor chlorine monoxide concentration in the stratosphere, since the short-lived ClO is a crucial intermediate participant in reactions involving destruction of stratospheric ozone.

Menzies, R. T.↗
NASA NTRS1977

The quadrupole coupling constant of HNC

The letter reports resolved measurements of the quadrupole hyperfine structure of HNC (hydrogen isocyanide). These measurements were made in the direction of the cool interstellar dust cloud L134, and were used to make an experimental determination of a fundamental spectroscopic constant of HNC, its quadrupole coupling constant.

Snyder, L. E.↗
NASA NTRS1979

Global operators for delta functions - Extension to scattering states and the inclusion of spin

The paper presents an extension of the identities of Hiller, Sucher, and Feinberg for the evaluation of bound-state matrix elements of delta function operators, to scattering states. Attention is given to the technical difficulties encountered in the application of the scattering-state identities and how they can be overcome, including infrared singularities which arise if Coulomb forces are present and the velocity of the incident particle is small. In addition, both the scattering and bound-state identities are generalized to include spin-dependent contact interactions and spin-dependent Hamiltonians. Finally, it is stressed that the identities can be used to improve the accuracy of calculations of interest for diverse physical phenomena, ranging from positron annihilation to hyperfine structure.

Sucher, J.↗
NASA NTRS1981

A new global operator for two-particle delta functions

A new type of global operator to be used in evaluating matrix elements of two-particle delta functions is introduced. It is based, like the Trivedi one-particle operator, on the Poisson equation and is easier to apply than the method of Hiller, Sucher and Feinberg. After a test in the helium isoelectronic sequence, the new method is applied successfully to the interesting problem of hyperfine structure in muonic helium.

Drachman, R. J.↗
NASA NTRS1985

Laboratory and astronomical detection of the deuterated ethynyl radical CCD

Two rotational transitions of CCD, N = 1-2 at 144 GHz and 2-3 at 216 GHz, were detected in a laboratory glow discharge through deuterated acetylene and helium, after which one, N = 2-1, was detected toward the rich molecular cloud behind the Orion Nebula. The 144 GHz transition is a well-resolved spin doublet split by 55 MHz, the components of which contain hyperfine structure of the order of 1 MHz, so far only partially resolved. From observations toward two positions in Orion, at and near the Kleinmann-Low nebula, the column density of CCD is determined to be 1.8 x 10 to the 13th/sq cm and the isotopic ratio CCD/CCH = 0.05. CCD was not detected at two positions in TMC-1.

Vrtilek, J. M.↗
NASA NTRS1986

A polarisation correlation study of the excitation of the H2 d3Piu (v1 = 0, N1 = 1) level by electron impact

Full details are given of an experiment in which the three normalized Stokes' parameters characterizing the decay of the electron impact excited d3Piu (v1 = 0, N1 = 1) rotational level of H2 were determined in an electron-photon coincidence experiment at 25 eV impact energy and over the angular range of 20-60 deg. An analysis shows how these parameters are related to the state multipoles characterizing the excited state. The rather low degree of coherence which was observed is consistent with various depolarizing effects, namely the averaging over magnetic sublevels which occurred in both the excitation and decay channels and also the perturbations due to fine and hyperfine structure relaxations.

Mcconkey, J. W.↗