Optical Spectral Lines Research Articles

Infrared diode laser spectroscopy of high-temperature molecules using spectrum processing by Fourier transformation

A heat-pipe high-temperature cell of the White cell type was constructed for sensitive detection of the spectra of high-temperature molecules. It has been incorporated into the optical system of a tunable diode laser spectrometer. With a 40 m optical path length abundant spectral lines of the Δν=2 vibration—rotation bands of NaBr have been observed in the wavenumber range between 560 and 600 cm −1. The technique of spectrum processing by use of Fourier transformation was applied to the source-modulated diode laser spectrum to eliminate fringes and to improve the signal-to-noise ratio.

Optical properties of quasars – I. Observations

A large set of spectra of low-redshift, radio-loud quasars at low resolution (20-25 A) is presented. The spectral range covers most of the important optical spectral lines, ranging from Hα 6562 A in some objects to [Ne v] 3426 A in others. The sample has the advantage of being observed and reduced in a uniform manner, as well as being considerably larger than previous surveys of radio-loud quasars.

Quiescent chromospheric response to the (E)UV/optical flare radiation field on dMe stars

We examine the response of the quiescent chromosphere to the large (E)UV and optical continuum and spectral line radiation field arising from a flare. We show that during a UV Ceti type flare, which displays a large U-band enhancement, a major part of the Balmer line flux may arise from the “quiescent chromosphere”, rather than the heated flare plasma itself. This leads us to distinguish two main phases in the Balmer lines, as first proposed by Houdebine et al. (1989): an early, mainly impulsive, phase, driven by radiative pumping of the quiescent chromosphere, which is mainly correlated with continuum variations, and a later one, related to the thermal flare phase, which arises from the cooling of the flare plasma itself. The effect of the radiative pumping is much larger for stellar (dMe) than for solar flares, due to substantial differences in the flare, relative to the quiescent, level and the quiescent chromospheric density and temperature.

Optical Chromospheric Spectral Lines in K and M Dwarf Stars

AbstractObservations are reported of the Ca II resonance lines and II α in dK and dM stars, made with high S/N ratio and high spectral resolution. Ca II emission is found in all stars observed, and those having weak Ca II exhibit marked Hα absorption. It is found that the strengths of the two kinds of chromospheric, lines are not tightly correlated, an effect which can be shown to be independent of the effective temperature of the stars. The result implies that a one-parameter description (e.g. heating rate) of the chromospheres is not viable. While lateral inhomogeneities are likely to be an important second parameter, we also suggest that the Hα line may be formed in a region considerable higher that in which the Ca II lines are formed.

On the nature of the relationship between inhomogeneously broadened phosphorescence and ODMR spectral lines

The nature of the inhomogeneous broadening of optical and ODMR spectral lines of aromatic molecules hosted in low temperature glasses is experimentally and theoretically investigated. Particular attention is paid to the relationships which exist between the various classes of inhomogeneously broadened spectral lines, and the salient features are illustrated with the results of ‘‘site selection’’ spectroscopy. A theoretical formalism based on the assumption of a uniform ‘‘solvent field’’ is presented and used to account for the major experimental features. Various ODMR line broadening mechanisms are considered and their relative importance evaluated.

Precision Measurements of the Rydberg Constant

Five recent measurements of the frequencies of optical spectral lines in atomic hydrogen and deuterium have improved the accuracy of the Rydberg constant beyond 1 part in 109. We review these experiments and discuss the importance of the Rydberg constant in atomic theory and in relation to the other fundamental physical constants. We discuss the limitations of these recent experiments as well as the future of Rydberg constant measurements.

A prompt radio burst from supernova 1987A in the Large Magellanic Cloud

Supernova 1987A in the Large Magellanic Cloud was discovered1 on 24 February 1987; optical observations define the geocentric time of the explosion to be between February 23.10 and February 23.443 UT2,3. The supernova rose quickly to a visual magnitude of about 4.2 and has remained near that level since. Optical spectral line observations4 show that the photosphere was initially expand-ing at ∼16,000 km s−1 and that the supernova is probably of Type II, that is, from a massive progenitor star. Its position is coincident with a 12th magnitude blue star5 but International Ultraviolet Explorer (IUE) observations6 suggest that this blue star may still be present. The supernova progenitor star may therefore have been a fainter companion to this star. Radio emission from the supernova was detected at Australian observatories within two days of the increase in optical brightness. Here we report information obtained at four frequencies, namely 0.843, 1.415, 2.29 and 8.41 GHz. At frequencies around 1 GHz the peak flux density was about 150 mJy and occurred within four days of the supernova. The event may be a small precursor to a major flare of the type previously observed in radio supernova.

Sources of electromagnetic radiation from fracture of rock samples in the laboratory

Rock, when fractured in the laboratory, emits electrical signals with a broad maximum in the power density spectrum in the band from 900 Hz to 5 kHz. Quartz‐free basalt rocks radiate both light and low‐frequency electrical signals as intensely as quartz‐bearing rocks, suggesting that the piezoelectric effect of quartz is at most a minor contributor to the total power radiated. Newly created rock surfaces acquire a local net charge distribution when exoelectrons are expelled and removed from the vicinity of the new surfaces by collisional and other processes. The rotational, vibrational, and linear motion of rock fragments with charged surfaces is the major contributor to the observed power density spectrum of the low‐frequency electrical signals. Neither optical spectral lines nor high‐frequency electromagnetic radiation, characteristic of electric discharges, occur at fracture. Exoelectron bombardment of the ambient fluid surrounding the sample, not electric discharge, is the excitation source for the light emitted at fracture.

Improved calculation of field isotope shift constants for optical spectral lines

Following the approach of previous investigations improved formulae for the field isotope shift constantCunif of optical spectral lines have been derived assuming a uniform nuclear charge distribution. From these formulaeCunif may be evaluated forselectrons with an accuracy of better than 1%. After considering the effect of the different normalization procedures the results obtained by different methods of approach are in good agreement.

Optical emission actinometry and spectral line shapes in rf glow discharges

Optical emission actinometry has been used recently as a means for estimating relative concentrations of radicals in rf plasmas. The technique relies upon normalization of the radical emission intensity to that from an inert gas (the actinometer) in order to compensate for changes in the electron density or energy distribution. However, actinometry is a valid measure of ground-state densities only when the excited states are created by electron-impact excitation (e.g., as opposed to chemiluminescent reactions or electron-impact dissociation). When techniques such as laser-induced fluorescence and optical-absorption spectroscopy are available, there is little need to use actinometry. However, there are many instances where these techniques are not yet applicable or practical and the use of actinometry may be desirable. In such instances, a simple means of assessing the validity of an actinometer would be advantageous. We describe the use of emission line shapes for determining the mechanism of excited-state formation and assessing the validity of an actinometer. In CF4/O2/Ar plasmas, both Ar* and F* are created with cold (360±70 K) translational distributions over a range of [F] from 0.4 to 4.0×1014 atoms cm−3. This implies that both species are created by electron-impact excitation and that Ar can be used as an actinometer in determining [F]. In Cl2/Ar plasmas, however, Cl* and Ar* emission line shapes in the sheath show substantial broadening during the cathodic part of the rf cycle, which implies that other excitation mechanisms such as dissociation, attachment, ion impact, and charge exchange are important and that actinometry is not valid under these conditions. But, time-averaged Cl* and Ar* emissions in the discharge center have identical linewidths, so that actinometry can be used to determine Cl atom concentrations.

VLA observations of the optical jets and nucleus of NGC 1097

Failure to detect the extended optical jets of NGC 1097 at 20 cm leads us to conclude that these jets are not the consequence of synchrotron emission, but rather of thermal bremsstrahlung emission. The flat spectrum at optical and near-infrared wavelengths and the lack of optical spectral lines set a lower temperature limit for the hot gas, while a null detection at X-ray wavelengths sets an upper temperature limit. The coincidence of these limits requires the gas to be at approximately 106 K. The electron density is about 2 cm−3. The emitting plasma is probably ambient material piled up by particles ejected from the nucleus of NGC 1097. A phenomenon which is apparently unrelated is a bright ring of non-thermal emission at a radius of 580 h−1 pc from the nucleus of NGC 1097. This ring is coincident with a ring of optical hotspots and with 10 µm emission, and can be understood in terms of a model which invokes vigorous star-formation and supernova production.

On the calculation of field isotope shifts for optical spectral lines

An additional factor of (n/N)3 has to be included in the usual procedure for deducing the change in mean square nuclear charge radii from optical field isotope shift measurements, n and N being the principal and the relativistic quantum number of the s-electron respectively. This correction amounts to about 8 % for heavy atoms as for example Hg leading to better agreement between results from optical field isotope shift measurements and from electronic and muonic X-ray data.

Operation modes and its optical measurements of plasma stream transport system

The plasma stream transport method is a method where material transport is caused to occur in a plasma stream contained in a magnetic flux pipe. As the plasma stream contains only ions and electrons, the optical emission spectral lines from the plasma stream are considered to be representative of the material constituents of the plasma stream. A prototype plasma stream transport system was constructed and operated in three configurations or modes. The emission pattern was observed to depend on the operating mode and the measuring position along the plasma stream. Transport rates were estimated for the three operating modes and evaluated in terms of the optical emission measurements. The spectral lines at the vicinity of the substrate were found to correspond to the constituent of the deposition film.

Registration of Low Intenstity Spectral Lines with Fabry Perot Interferometer by Photon Counting Method

Abstract A simple photon counting system for measuring very low optical spectral lines is described. It is of interest the cooling housing for its low cost and easy implementation. A comperison between the standard d. c. registration system and the photon counting one is given.

Optical Line Studies of the Nuclei of NGC 4945 and 5128

Microwave line investigations have shown that several bright southern galaxies contain dense molecular clouds overlying bright radio nuclei (see e.g. Whiteoak 1978). In terms of general kinematic models of galaxies the clouds have velocities that are anomalous, being consistent with radial motions both towards and away from the nucleus. To extend our knowledge of these motions we are investigating the distribution of optical spectral lines near the nuclei of the galaxies. We present here preliminary results for NGC 4945 and 5128.

On the stellar velocity of long-period variables and OH maser stars

view Abstract Citations (34) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the stellar velocity of long-period variables and OH maser stars. Reid, M. J. Abstract A statistical analysis of both optical and microwave spectral lines of long-period variable/molecular maser stars indicates that, contrary to long-held theories, the stellar radial velocity is not associated with either the high-velocity OH maser emission features or the optical absorption lines. The results presented in this paper, coupled with those deduced from recent millimeter observations, place the stellar radial velocity between the two OH maser features and between the optical emission and absorption lines. This supports models of these objects in which OH emission comes from the approaching and receding sides of an expanding circumstellar envelope. Publication: The Astrophysical Journal Pub Date: August 1976 DOI: 10.1086/154548 Bibcode: 1976ApJ...207..784R Keywords: Hydroxyl Emission; Maser Outputs; Microwave Spectra; Radial Velocity; Stellar Motions; Variable Stars; Absorption Spectra; Astronomical Models; Emission Spectra; Line Spectra; Millimeter Waves; Astrophysics full text sources ADS | data products SIMBAD (37)

The separation of mass and field effects in optical isotope shifts

A method has recently been proposed for the separation of mass and field effects in optical spectral lines, using only optical data obtained for two such lines. This is demonstrated to be invalid.

Effect of High-Intensity Microwave Radiation on Optical Transitions of Atomic Hydrogen

Interaction of atomic systems with high intensity monochromatic microwave radiation leads to characteristic splittings of optical spectral lines