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Results for “ZEEMAN EFFECT”

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Zeeman effect of P II.

An investigation was conducted of the Zeeman effect of PII because it provides unique J-value assignments together with a sensitive check on the accuracy of wave functions obtained from least-squares fitting of energy levels. About forty new lines were added to the spectrum, and g values were obtained for 76 levels of PII. By incorporating this new experimental material in a systematic program of least-squares calculations, supplemented by ab initio calculations, it was possible to complete the description of the 3p5p and 3p5d configurations.

Li, H.↗
NASA NTRS1985

Trends in measurement of solar vector magnetic fields using the Zeeman effect

Trends in spectropolarimetry as applied to the problem of Zeeman effect measurement are discussed. The use of detector arrays to improve observing efficiency is obtained. Which required new polarization modulation schemes that match the time required to read detector arrays. Another significant trend is narrowband filters, to improve angular and temporal coverage, and to Fourier transform spectrometers, to improve spectral coverage and precision. Low-polarization designs and improved methods for compensating instrumental polarization were developed. A requirement for high angular resolution suggests using adaptive optical devices to subdue the effects of bad seeing. The ultimate strategy to beat the seeing is to loft the telescope above the atmosphere such as is planned with a 30-cm telescope in 1985 and a 1250-cm telescope in 1990.

Harvey, J. W.↗
NASA NTRS1973

Zeeman effect in the X-ray star candidates HD 77581 and theta super 2 Orionis.

The discovery of Zeeman effects is reported in HD 77581 and theta super 2 Orionis, optical candidates for the X-ray sources Vela XR-1 and 2U 0525-06, respectively. The maximum longitudinal magnetic fields recorded were -10,000 G in HD 77581 and +1500 G in theta super 2 Ori. Various polarimetric data are also given, including evidence for a variable linear polarization in HD 77581.

Kemp, J. C.↗
NASA NTRS1972

Zeeman effect of As II.

Spectrograms of As electrodeless-discharge tubes operated in a field of 24,025 G have given Zeeman patterns for 232 As II spectral lines from 2361 to 10,556 A and yielded 80 Lande g factors, of which more than half are new. There is agreement between these and the g values calculated by least-squares fitting for single configurations or for multiconfigurations, where configuration interaction is noticeable. All of the measured g values as well as the energy levels are used in the fitting process.

Li, H.↗
NASA NTRS1992

The Zeeman effect in astrophysical water masers and the observation of strong magnetic fields in regions of star formation

The present study solves the transfer equations for the polarized radiation of astrophysical 22-GHz water masers in the presence of a magnetic field which causes a Zeeman splitting that is much smaller than the spectral line breadth. The emphasis is placed on the relationship between the recently detected circular polarization in this maser radiation and the strength of the magnetic field. When the observed spectral line breadth is smaller than about 0.8 km/s (FWHM), it is calculated that the uncertainty is less than a factor of about 2. The accuracy is improved significantly when the angle between the line of sight and the direction of the magnetic field does not exceed about 45 deg. Uncertainty in the strength of the magnetic field due to lack of knowledge about which hyperfine transition is the source of the 22-GHz masers is removed. The 22-GHz maser feature is found to be the result of a merger of the three strongest hyperfine components.

Nedoluha, Gerald E.↗
NASA NTRS1990

Symbolic description of periodic orbits for the quadratic Zeeman effect

The organization of the periodic orbits of a hydrogen atom in a uniform magnetic field is studied. It is shown that the dynamics is qualitatively different from that for weak fields and negative energies. The orbits can be mapped one-to-one onto a ternary symbolic tree, an organization which turns out to be applicable for all values of energy and field strength. The results indicate that the field-free hydrogen atom has a purely chaotic limit for positive energies.

Eckhardt, Bruno↗
NASA NTRS1994

Intensity-dependent circular polarization and circumstellar magnetic fields from the observation of SiO masers

A new aspect of the propagation of astrophysical maser radiation in the presence of a magnetic field is described in which circular polarization is created. The resulting antisymmetric spectral line profile for this circular polarization resembles that produced by the ordinary Zeeman effect when the Zeeman splittings are much less than the spectral line breadth. It is caused by the change, with increasing maser intensity, in the axis of symmetry for the molecular quantum states from a direction that is parallel to the magnetic field to a direction that is parallel to the direction of propagation. When the maser is radiatively saturated, and the rate for stimulated emission is within an order of magnitude of the Zeeman splitting in frequency units, this 'intensity-dependent circular polarization' is greater than that due to the ordinary Zeeman effect by factors as large as 1000. The circular polarization that is observed in the spectra of circumstellar SiO (J = 1-0) masers associated with late-type giants and supergiants may then be caused by magnetic fields as weak as about 10 mG. With the standard Zeeman interpretation of the observations, magnetic fields of 10-100 G are indicated. The lower fields are similar to the limits obtained from the observation of the 22 GHz water masers which are typically somewhat further from the central star. The observed tendency for the fractional linear polarization of SiO masers to increase with increasing angular momentum of the molecular state is shown to be a likely result of anisotropic pumping. Errors are identified that invalidate a recent conflicting claim in the literature about the basic theory of maser polarization in the regime that is relevant here.

Nedoluha, Gerald E.↗
NASA NTRS2003

Linear Polarization Measurements of Chromospheric Emission Lines

We have used the Zurich Imaging Stokes Polarimeter (ZIMPOL I) with the McMath-Pierce 1.5 m main telescope on Kitt Peak to obtain linear polarization measurements of the off-limb chromosphere with a sensitivity better than 1 x 10(exp -5). We found that the off-disk observations require a combination of good seeing (to show the emission lines) and a clean heliostat (to avoid contamination by scattered light from the Sun's disk). When these conditions were met, we obtained the following principal results: 1. Sometimes self-reversed emission lines of neutral and singly ionized metals showed linear polarization caused by the transverse Zeeman effect or by instrumental cross talk from the longitudinal Zeeman effect in chromospheric magnetic fields. Otherwise, these lines tended to depolarize the scattered continuum radiation by amounts that ranged up to 0.2%. 2. Lines previously known to show scattering polarization just inside the limb (such as the Na I lambda5889 D2 and the He I lambda5876 D3 lines) showed even more polarization above the Sun's limb, with values approaching 0.7%. 3. The O I triplet at lambda7772, lambda7774, and lambda7775 showed a range of polarizations. The lambda7775 line, whose maximum intrinsic polarizability, P(sub max), is less than 1%, revealed mainly Zeeman contributions from chromospheric magnetic fields. However, the more sensitive lambda7772 (P(sub max) = 19%) and lambda7774 (P(sub max) = 29%) lines had relatively strong scattering polarizations of approximately 0.3% in addition to their Zeeman polarizations. At times of good seeing, the polarization spectra resolve into fine structures that seem to be chromospheric spicules.

Sheeley, N. R., Jr.↗
NASA NTRS1980

Zeeman degeneracy effects in collisional intense-field resonance fluorescence

Resonance fluorescence due to intense laser fields from a Zeeman degenerate atom being perturbed by collisional interactions is calculated in the impact regime by using the quantum-fluctuation-regression theorem. Various interesting effects are found. For example, the scattered intensity spectrum for a J = 0 to J = 1 transition for polarization parallel to the laser polarization is essentially an asymmetric triplet, whereas for a perpendicular polarization due to collisions the spectrum is essentially a doublet (whose frequencies do not correspond with any of those of the triplet). Further, the width of the fluorescent component (whose frequency is close to the unperturbed frequency) actually decreases with increasing laser power.

Cooper, J.↗
NASA NTRS1986

Measurements of magnetic fields in solar prominences

Magnetic fields can be measured, in solar prominences, by means of two different basic mechanisms that are responsible for the introduction (or the reduction) of a given amount of polarization in spectral lines: these are the Zeeman effect and the Hanle effect. Through the splitting of the magnetic components of a spectral line, the Zeeman effect is capable of introducing a certain amount of circular polarization across the line profile. The Hanle effect consist of a modification of the linear polarization that is induced in spectral lines by the anisotropic illumination of the prominence plasma by the photospheric radiation field. These two effects are briefly discussed.

Deglinnocenti, Egidio Landi↗
NASA NTRS2022

Coronal Polarimetry: Determining the Magnetic Origins of Coronal Mass Ejections

Synopsis: The mechanism for the release of stored magnetic energy in solar eruptions remains a major unsolved problem of Heliophysics. Choosing between triggers requires knowledge of pre-eruptive magnetic fields (B). Although linear polarization in visible/infrared (VIR) coronal emission lines reveals intriguing clues about coronal mass ejection (CME) precursor topology, small telescope apertures limit current capability for measuring vector field. Current coronal observations are insufficient to diagnose 3D coronal magnetic fields in CME precursors. Coronal cavities are the ideal candidates for CME precursor studies. BLOS in cavities is a direct measure of stored magnetic free energy, and the presence and location of topological X-points (reconnection locations) and O-points (circulation of B about axis) distinguish predictions of the flux rope-torus-instability and sheared-arcade-breakout CME models. - Finding: Coronal cavities are ubiquitous throughout the solar cycle, erupt as CMEs, and have coronal polarimetric signatures that distinguish between model predictions. - Recommendation: Coronal cavities should be targeted in a comprehensive multiwavelength study of CME precursors & associated eruption-driving mechanisms. Large ground-based VIR telescopes can measure both coronal magnetic field topology and strength through a combination of the saturated Hanle and BLOS -sensitive Zeeman effects. - Finding: The 4m Daniel K. Inouye Solar Telescope (DKIST) and proposed 1.5m Coronal Solar Magnetism Observatory Large Coronagraph (COSMO-LC) make a major leap forward in VIR coronal sensitivity, enabling measurement of vector B. - Recommendation: A dedicated coronal synoptic telescope with a large field-of-view (i.e., COSMO-LC) is needed to identify the dominant CME driving mechanisms, by measuring coronal magnetic fields from precursor state into eruption. In the UV, a new opportunity has arisen to make use of the strong H I Lyman-α coronal line, which obtains a measurement of B that is independent of the Zeeman effect. - Finding: Small-telescope spectropolarimetric capability in the unsaturated Hanle regime provides an independent and complementary coronal magnetic diagnostic to large ground-based telescope measurements. - Recommendation: The proposed 12-cm Coronal Lyman-α Resonance Observatory (CLARO) spectropolarimetric coronagraph demonstrates a path forward for space-based observations of the coronal magnetic field that should be incorporated into future missions away from the Sun-Earth line (e.g., COMPLETE).

magnetic energy↗