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Topic: Spectral line

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In the News (Mon 16 Oct 17)

  Spectral Line Modes
Any number of spectral line channels that is a power of 2, that is less than or equal to the number in the table and that is greater than or equal to 2 may be selected using the data selection options available within the
Any number of spectral line channels that is a power of 2, that is less than or equal to the number in the table, and that is greater than or equal to 2 may be selected using the data selection parameters available in the
Spectral line dynamic range is commonly defined as the ratio of the peak brightness in the strongest channel to the minimum detectable line brightness in an image.
www.vla.nrao.edu /astro/guides/vlas/current/node35.html   (1169 words)

 comet spectral line comet spectral line comet spectral line comet spectral line comet spectral line comet spectral line ...
Spectral lines are emitted at optical wavelengths through "resonance fluorescence".
Photons from the sun are absorbed by an atom or "radical" (a piece of a molecule already photodissociated by a higher energy solar photon).
The state of rotation is largely determined by the combined effects of thermal motions in the gas (communicated through collisions between molecules) and the absorption of photons from the sun.
www.ifa.hawaii.edu /faculty/jewitt/spectral-excitation.html   (192 words)

 NIST: Atomic Spectros. - Spectral Line Shapes, etc.
Observed spectral lines are always broadened, partly due to the finite resolution of the spectrometer and partly due to intrinsic physical causes.
The principal physical causes of spectral line broadening are Doppler and pressure broadening.
line at 4861 Å, widely used for plasma diagnostics, is tabulated in the table below for some typical temperatures and electron densities [33].
physics.nist.gov /Pubs/AtSpec/node20.html   (473 words)

 JPL Molecular Spectroscopy
In the gas phase at low pressures, molecules exhibit absorption in narrow lines which are very characteristic of the molecule as well as the temperature and pressure of its environment.
The precise frequencies of these lines can be fit to quantum mechanical models which can be used both to determine the structure of the molecule and to predict the frequencies and intensities of other lines.
Line files are designated as ctttttt.cat, where tttttt is the zero-filled catalog tag number (the first entry in each line of the catdir.cat file).
spec.jpl.nasa.gov   (695 words)

 NIST Scientific and Technical Databases - Online Scientific Databases
An atlas plot of the spectrum is given, with the spectral lines marked and their intensities, wavelengths, and classifications listed.
All of the rotational spectral lines observed and reported in the open literature for 121 diatomic molecules have been tabulated.
All of the rotational spectral lines observed and reported in the open literature for 91 hydrocarbon molecules have been tabulated.
www.nist.gov /srd/online.htm   (1695 words)

 CFA Scientific Divisions: AMP: Databases
ATOMDB: Chanda X-Ray Center atomic database for X-ray plasma spectral modelling.
Line ID tool (also lists information about selected atomic transitions)
This is a list of relevant databases maintained elsewhere.
cfa-www.harvard.edu /amdata/ampdata/kurucz23/sekur.html   (88 words)

  Heterodyne Observing
JPL spectral line catalog browser form; and explanation of use
Reducing single spectrum JCMT spectral line data with AIPS++.
Spectral line fivepoints are a valuable extension to the usual continuum technique using the CBE.
www.jach.hawaii.edu /JCMT/spectral_line   (628 words)

  Spectral line Summary
The spectral lines observed in the absorption and emission spectra of atoms or molecules are the result of transitions occurring between different energy levels as electromagnetic radiation is absorbed or emitted.
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies.
Spectral lines are the result of interaction between a quantum system (usually atoms, but sometimes molecules or atomic nuclei) and single photons.
www.bookrags.com /Spectral_line   (1865 words)

 spectral line concept from the Astronomy knowledge base   (Site not responding. Last check: )
The essential difference between optical line spectra and X-ray spectra is that the former correspond to energy changes in the outer electrons in an atom, and the latter to energy changes in the inner electron orbitals.
Like emission lines, absorption lines betray the chemical composition and velocity of the material that produces them., Dark line superposed on a continuous spectrum, caused by the absorption of light passing through a gas of lower temperature than the continuum light source.
spectral series line (22 kinds, 82 facts) - A spectral line belonging to a series of lines of a given atom arising from transitions with a common lower energy level.
www.site.uottawa.ca:4321 /astronomy/spectralline.html   (562 words)

 Spectral Analysis - What Do They Tell Us?   (Site not responding. Last check: )
However, this is not true when the star is moving towards us (the lines are observed at shorter wavelengths, or 'blueshifted, than those measured in the laboratory) or moving away from us (observed at longer wavelengths, or 'redshifted').
An emission line at 587.6 nm was first observed in the Solar corona during the eclipse of 1868 August 18th, although the precise wavelength was difficult to establish at the time (due to the short observation using temporary set-ups of instruments transported to Asia).
She applied the up-to-date theory of spectral line formation, and found that the chemical compositions of stars were probably all similar, the temperature being the important factor in creating their diverse appearances.
imagine.gsfc.nasa.gov /YBA/cyg-X1-mass/spectral-info.html   (1559 words)

 Stellar Properties from Spectral Lines - Intro
The spectral lines of a star contain a wealth of information because their formation is sensitive to the conditions present in the star's atmoshere.
The spectral lines are formed by the absorption of photons as electrons jump from a lower energy level to a higher one.
Again, as with temperature, if you look at lines due to atoms in two different ionization states, you can calculate the number of absorbers which must be present (given the temperature and surface gravity which derermine how many of the atoms have electrons in the proper energy level to cause the spectral line).
www.phys.uwosh.edu /mike/exercises/lines/lines.html   (1941 words)

 MPIfR Sub(mm) Group Science -- Spectral line surveys
In fact, unbiased spectral line surveys are necessary to obtain an unbiased view of the chemistry of a specific region.
We assume that the line emission of each molecule is a superposition of several radiatively non-interacting components, each of which can be described by a source size, column density, velocity width, velocity offset and a single rotation temperature.
The disadvantage of all deconvolution methods is that pointing shifts result in line shape and strength changes for the various measurements of the same line (due to the structured source), which results in spurious features in the synthesized SSB spectrum.
www.mpifr-bonn.mpg.de /div/mm/science/survey.html   (1943 words)

 Algorithms: Spectral line fits - SDSS DR2
Separate continuum and flux windows are used to determine spectral line indices analogous to the Lick indices.
Line indices are invariant under transforming from observed to rest frame.
Since the line fits are allowed to drift in wavelength somewhat, the exact precision of the lines are not important.
www.sdss.org /DR2/algorithms/speclinefits.html   (885 words)

 Function: remove_spectral_lines()
If set to zero, then to save time in situations where all that is needed a list of spectral lines and their amplitudes and phases, then neither of the amplitude spectra are calculated.
In situations where all that is needed is a list of spectral lines and their amplitudes, and it is desired to limit the search to a restricted range of frequencies, then
To ensure that we do not remove the same line twice, the spectral line associated with each spectral line on the working list is subtracted from the data-set, provided that it does not lie within a frequency width of of a stronger (larger F-value) line.
www.lsc-group.phys.uwm.edu /~ballen/grasp-distribution/GRASP/doc/html/node306.html   (780 words)

 E1622-94(1999)e1 Standard Practice for Correction of Spectral Line Overlap in Wavelength-Dispersive X-Ray Spectrometry ...
Procedures are given for the correction of line overlap interferences encountered in the analysis of metallic and nonmetallic specimens in wavelength dispersive X-ray spectrometry.
The interfering line or lines may be from the same spectral order as the analyte line or may be from another spectral order.
Interfering lines from the X-ray tube and associated instrumental components are usually specific to the system and the procedure for dealing with these may be found elsewhere.
www.astm.org /DATABASE.CART/PAGES/E1622.htm   (331 words)

 Spectral Analysis - Search Results - MSN Encarta   (Site not responding. Last check: )
Spectral Analysis, investigation of the distribution of energy emitted by a radiant source, such as visible light, arranged in order of wavelengths....
Astronomers can see the different wavelengths of light of a star in more detail by looking at its spectrum.
Spectral Line, isolated bright or dark line in spectrum produced by emission or absorption of light of a single wavelength.
encarta.msn.com /Spectral_Analysis.html   (142 words)

 SOUP Tuneable Filter User's Manual
These are tuning values for given spectral lines that will be observed in a sequence which is coordinated with the science camera (see Section 5).
The line center tunings for all available spectral lines have been calibrated in the laboratory and stored in a file called "filt.dat" in the TF source code directory.
TF line calibration consists of placing the photometer behind the filter and recording light levels as the filter is tuned through a specified range around a given line.
www.solarphysics.kva.se /LaPalma/SOUP_Users_Manual/SOUP_users_manual.html   (4873 words)

 Spectral Computers PC Solutions
Spectral Computers are designed to maximize the throughput of AV data, providing the features required by today's audio creation software.
The Spectral range is able to process significantly more AV data at higher speeds, while the installed Windows XP operating system has been deeply optimized to clear out unnecessary features and applications.
Spectral Computers are based on an open architecture, which allows a system to be upgraded as performance needs increase.
mixonline.com /mixline/spectral-pc-solution/index.html   (301 words)

The study of spectral lines is known as spectroscopy and is heavily used in astronomy.
By studying how their spectral lines are shifted by their motions with respect to Earth, scientists can determine not only their characteristic motions but also estimate the forces responsible, particularly gravity.
Finally, since spectral lines reveal the presence of specific atoms and molecules in space, these same components can serve as tracers of the physical conditions in their surroundings, particularly those of temperature, density, and pressure.
archive.ncsa.uiuc.edu /Cyberia/Bima/CBCSpecLines.html   (528 words)

 Energy levels, wavelengths, transition probabilities
Atomic data for permitted resonance lines of atoms and ions from H to Si, and S, Ar, Ca and Fe.
The compilation covers all wavelengths longward of the He II Lyman limit at 227.838 A and all the ion states of all elements from hydrogen to bismuth (Z=83) for which reliable data are known.
Observed lines and lines in the CHIANTI database between 50 and 1100 A Dere et al.
www.pa.uky.edu /~verner/lines.html   (557 words)

 Scheduling EVN spectral line observations
Note that target lines should be located close to the center of the frequency band because the band edges have lower sensitivity and can have large phase offsets.
If a line source has a wide velocity coverage, overlapping a part of the frequency (velocity) coverage between two frequency bands may be a good idea to see a part of the line components in the two bands.
When several line sources are observed with different frequency setups in one observation, AIPS requires bandpass calibrators to be observed with the same setups, so independently for each target.
www.evlbi.org /scheduling/evn_line.html   (1039 words)

 Spectral DNC from Divine Skin
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vitanetonline.com /description/327398/vitamins/Spectral-DNC   (509 words)

 3.11 Spectral line mapping
The principles of post-correlation spectral line data reduction are no different from multi-channel continuum processing.
The experiment must be designed so that on either side of the line emission there are sufficient continuum-only channels which will give a high enough signal to noise ratio (when added together) to subtract the continuum accurately.
The general procedures are similar to §3.8.8 but the bp-cal and the target and any other sources to be processed in line mode must be carefully inspected for interference at an early stage in data processing.
www.merlin.ac.uk /user_guide/OnlineMUG/newch0-node59.html   (492 words)

 Spectral Line Observations
Experience over the years with spectral line VLBI has shown this to be the preferred observing mode since it minimizes the chances of mistakes at stations that do not have automatic frequency setting.
Typically velocities for radio spectral lines in galactic sources are given in the radio definition in the LSR frame.
The example below shows the SCHED input for a spectral line It is a modified version of the file used for a project by Phil Diamond in Dec 95.
www.aoc.nrao.edu /~cwalker/sched/sched/node36.html   (2133 words)

 Spectral Line Shape Studies at Toronto   (Site not responding. Last check: )
Although the absolute frequency accuracy is limited to.02 /cm 600 MHz by the variation (daily) of the frequency of the ion laser and the accuracy of the wavemeter in the dye laser, we routinely measure pressure shifts with a 10 MHz accuracy relative to the line origin.
In addition to improving our understanding of line shape models, measurements of the line widths and integrated intensities are relevant to such fields as atmospheric pollution studies.
Recently completed research includes line shift and width measurements of depolarized Q branch spectra in D2, line shift measurements in C02, non-Lorentzian features in the P and R branches in CO, line mixing in D2, and the widths and shifts of the vibrational O and S branches in D2 at 100K.
www.atmosp.physics.utoronto.ca /MOLSPEC/spectral_line_shapes.html   (433 words)

 4.2 Spectral line modes   (Site not responding. Last check: )
Spectral line observations with the GBT can be performed with all currently-available receivers.
The Spectral Processor is the backend of choice only for observations plagued by high levels of RFI but which don't require wide bandwidths or a large number of spectral channels.
If the difference is smaller than about one half the observing bandwidth (called in-band frequency switching), it is in many cases possible to increase the signal-to-noise of the observation by a sqrt(2) by averaging the 'on' and 'off' frequency measurements.
www.gb.nrao.edu /GBT/GBTMANUAL/node17.html   (762 words)

 UVCS Line-fitting toolkit
Fits line profile to the data taking into account the instrument model, assuming that coronal emission can be modeled by one or two Gaussian profiles.
This function retrieves data for the spectral lines with given wavelengths WL (in angstroms) from exposure EXP in WS.
On the plot this assumption is indicated by word "TIED" for line width in line description - it means that the width is the same as for corresponding component in another line.
cfauvcs5.harvard.edu /UVCS/LINE_FITTING/SULFIT.html   (1504 words)

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