NIST Atomic Spectra Database Help Page
General Information
- Introduction to the ASD database
- Introduction to Atomic Spectroscopy
- List of Holdings
- ASD Data
- Navigation
- Searching for Data
- Options for Viewing Data
- Using WWW Browser Features
- Special Configuration and Term Notations for ASCII Output Files
- Locating references in the ASD Bibliography
-
- Lines Search Form
- Wavelength ordered searches (including examples)
- Multiplet ordered searches (including an example)
- Selecting Spectra for Lines Searches (including examples of spectral notation)
- Setting Options for Lines Searches
- Setting Output Preferences
- Setting Additional Criteria
- Output for Lines (description of columns of output)
-
- Energy Levels Search Form
- Selecting Spectrum for Levels Searches
- Setting Additional Criteria
- Output for Levels (description of columns of output)
Two lists of holdings are available. One for lines data, the other for levels
data. Either of these lists may be accessed by selecting "List of
Spectra" in the menu bar and then selecting the appropriate "List of
Holdings" link.
The List of Holdings for lines data shows the following pieces of information:
- Total number of lines of data for the selected element.
- Number of lines with transition probabilities.
- Number of lines with level designations.
The List of Holdings for levels data shows the source of the data, either NIST
or unpublished compilations by R.L. Kelly.
The level tables compiled by R.L. Kelly are:
He II, Li, Be (except
Be I), B, F, Ne
(except Ne I), and Cl
(except Cl I and Cl II),
and Ar, all of which have new NIST compilations in progress,
plus As, Se, and Br.
All other levels in ASD have been critically compiled by NIST.
I. What Data Sources are included in ASD?
Our basic policy is to include in ASD only those atomic data which have been
critically evaluated by NIST. The main exceptions to this are the energy level
data compiled by R.L. Kelly for He II, Li, Be
(except Be I), B, F, Ne (except
Ne I), and Cl
(except Cl I and II).
While the Kelly energy levels list are unpublished, many of the data contained
in them are included in his lines compilations, which have been published in
the Journal of Physical and Chemical Reference Data, under the auspices of NIST
(formerly NBS) and AIP. Still, they have not been critically evaluated by NIST,
and a disclaimer to this effect appears when energy level data for these
spectra is queried in ASD. Energy levels and wavelengths for many of the
above-mentioned spectra are presently being critically evaluated in an
Institute-of-Spectroscopy (at Troitsk)/NIST collaboration.
The advantage of this NIST-evaluated-only policy is that it affords a set of
quality reference data. The disadvantage is that critical compilations
inevitably lag behind the generation of new data. An extreme case of this lag
is that of transition probabilities for the lighter 20 elements (except C,N,O),
most of which are taken from NIST compilations that were published in the late
1960's. These data are currently being updated and extended. New results for
C, N, and O have already been published (listed in the "Bibliography"
section), and contain nearly an order of magnitude more transitions than the
original compilations. Hopefully computerized handling of electronic data will
cut this lag substantially in the future, but the increasing amounts of data
and decreasing number of personnel are likely to insure that the lag will
remain significant.
We note that the large majority of the older data has held up well in
comparisons with newer results, at least in the sense that the original
estimated accuracies have generally proven to be representative.
If you have reason to believe that any ASD value is incorrect, please send your
comments via E-mail to Feedback.
It would be helpful if the message included a copy of all the text contained in
the URL for the specific search. Our apologies to authors who have produced new
and/or improved values which are not yet included in ASD because critical NIST
compilations have not been performed for that spectrum since publication of the
new data.
II. Reasons for differences between NIST published and ASD values
There are several reasons why differences sometimes occur between quantities
published in NIST compilations and the NIST ASD database:
Factors that can affect energy-level and transition data:
- Some values have been corrected or updated since publication. Also, some
additional entries have been made since publication.
- Differences can of course also result from errors, either in the originally
published value or in the value given in ASD. If you have reason to believe
that an ASD value is incorrect, please sent them via E-mail to
Feedback. It would be helpful if
the message included a copy of all the text contained in the URL for the
specific search.
Factors that can affect transition data only:
- The data integration process for lines takes data from the most recently
compiled data source for each line. For example, only the transition
probabilities themselves are taken from the published transition probability
compilations. All the information for the lower and upper levels of each
transition are taken from the most current NIST compilations of energy levels
for the appropriate spectrum. The Ritz wavelengths, which are usually the
default wavelengths given by ASD, are derived from these level energies. Even
the transition probabilities themselves may differ from those in the older
compilations, because the values from the most recent NIST compilations are
used when available.
- The user may request that both the observed and Ritz wavelength, the latter
being derived from the difference in level energies (Both observed and Ritz are
only available only for spectra for which comprehensive line lists are
available, i.e., Be I,
O II, Ne I, Mg, Al, S,
Ar, and Sc. By default, however, only a single wavelength is available. When
both the upper and lower level energies are available, the Ritz wavelength is
listed, unless the observed wavelength has more significant figures than the
derived Ritz wavelength. If the wavelength is "observed" rather than
"Ritz", this is indicated by a "#" sign at the end of the
"Obs-Ritz" column, which is available but not listed by default.
- Small differences for wavelengths, , may also result from our uniform application of a) an
algorithm for determining for significant figures in Ritz wavelengths,
and b) the index of refraction in air. This can in turn result in small
changes in the transition probabilities, which depend on
3, and oscillator
strengths, which depend on .
The ASD home page provides links for the user to view the following:
- Lines Search Form
- Levels Search Form
- Introduction to the ASD database
- List of Spectra
- Ground States and Ionization Energies for Neutral Atoms (note that Ground
States and Ionization Energies for multiply ionized atoms are available via the
Atomic Spectroscopic Database (Version 2.0, Version 1.2)).
- References
- Help
Except for the home page, all pages of the database contain a menu bar at the
top which may be used to navigate to any portion of the database mentioned
above. For example, if the user is viewing the Levels Form and wishes to now
view the Lines Form, the words "Lines Form" in the menu bar may be
selected to access the Lines Form. If the user is viewing the Lines Form and
desires help, the word "Help" in the menu bar can be selected to
access the ASD Help page.
The ASD home page provides links for the user to access the
following home pages and databases:
- The NIST home page
- The Physic Laboratory home page
- The NIST Physics Laboratory Physical Reference Data home page.
- Atomic Energy Levels Data Center
- Data Center on Atomic Transition Probabilities and Line Shapes
- NASA Astrophysics Data System (ADS).
- NIST Standard Reference Data home page
In addition, links for other NIST Atomic Spectroscopic Data are provided:
- NIST Atomic Spectroscopic Database (Version 1.2)
- Bibliographic Database on Atomic Transition Probabilities
- Spectrum of Platinum Lamp for Ultraviolet Spectrograph Calibration
These home page links, in addition to the link to the ASD version history, are
only accessible from the ASD home page and not from within the database.
The ASD database provides two primary search forms for accessing
data. The Lines Search Form (referred to
as the Lines Form) provides access
to transition data for atoms and atomic ions (referred to as lines data).
The Energy Levels Search Form (referred to
as the Levels Form) provides access to
energy levels data for atoms and ions (referred to as levels data).
These forms require that the user fill in the spectrum/spectra of interest
(and for lines queries the wavelength region of interest)
and then select the "Retrieve Data" button.
Access to output options
(e.g., selection of HTML tabular output or ASCII output) and additional search
criteria (e.g., selection of an energy bound) is provided.
Defaults for Viewing Data
The ASD database provides the user with the option to view data as either an
HTML formatted table (which includes subscripts and superscripts) or as an
ASCII table. The default is to display the output as an HTML formatted table.
The ASD database provides the user with the option to view data either in its
entirety or in pages. The default is to display the output in its entirety,
i.e., as one output file that can be scrolled through.
By increasing the window size and decreasing the font size, it is possible to
view more data per screen.
Viewing Data as an ASCII Table
An advantage of viewing ASCII output is that it takes less time
to display ASCII output than formatted data. Another advantage is
that ASCII data may be downloaded into a spread sheet or other program
located on the client computer.
Both the Lines Form and the Levels Form, have a section for
"Output Options".
Under the "Output Options" section, next to the "Format output"
heading, the pull down menu can be used to select "ASCII (TEXT)".
Viewing Pages of Data
An advantage of viewing data one page at a time is that the column headings
are displayed at the top of each page of data.
Another advantage is that viewing smaller amounts of data is much faster
than viewing a large file of data in its entirety. A disadvantage of viewing
data one page at a time is that it may be more convenient to scroll through
one large file of data instead of waiting for the browser to load the next or
previous page.
Each page of data includes the current page number, the total number of
pages, and links to view the next page of data or the previous page of data.
The page size can be customized to accommodate variance in font size and screen
size.
To change the default so that output is displayed in pages that can be viewed
one at a time, follow the steps listed below.
- From either the Lines Form or the Levels Form, look for the section
labeled "Output Options".
- Under the "Output Options" section, next to the "Display output"
heading, use the pull down menu to select "in pages."
- The page size can be changed as needed.
Viewing Large Amounts of Data
The default is to display output as an HTML formatted table
in its entirety. There is a certain amount of overhead associated
with creating output containing a large number of lines of
data formatted as an HTML table. The speed with which search
results can be viewed by the user is a function of the following:
- the speed of the client computer,
- the amount of memory on the client computer,
- the amount of data,
- the number of columns of formatted output,
- the speed of the network, and
- the browser's ability to load and render formatted tables.
Note that in some cases, for searches returning a large amount of
output, some browsers may lock up or not
be able to display all the data correctly. If you have a problem
viewing a formatted table of data, choose one of the other display
options or limit the range of your search.
To ease the task of selecting the desired display option depending on the
number of lines of output, a page is displayed prompting the user for further
input if the following criteria are met:
- the search results in more than 100 lines of output, and
- the user is using the default of the output displayed in its entirety
as a formatted table.
The page prompts the user for their display preference (for the current
search only). Users with more capable systems, may opt to continue to display
all lines of output as a formatted table in its entirety. An advantage of
displaying all lines of output as a formatted table is that the user is able
to view the formatted data in its entirety. Another advantage is that the user
can use the browser's "find" capability to scroll down to a value of interest.
The disadvantage is that this option can be very slow. A considerable amount
of time will need to be spent loading the data into the browser, and
having the browser determine how to render the many columns of data.
Users with less capable systems, or users primarily interested in viewing the
first portion of the data, may opt to choose one of the following options:
- Display 100 lines (maximum page size) as a formatted table.
Two advantages of this option are that it is faster than viewing the formatted
data in its entirety and that the user is still able to view a large portion of
the data (100 lines) at a time. Another advantage is that the user is able to
see column headings displayed at the top of each page of data. The disadvantage
is that the user is not able to view the data in its entirety.
- Display 15 lines (or default page size) as a formatted table.
The advantages of this option are that it is relatively fast and that the user
is able to view formatted data. Another advantage is that the user is able to
see column headings displayed at the top of each page of data. The disadvantage
is that the user must view pages of data one by one.
- Display output as an ASCII table.
This option has the advantage that it is relatively fast. The browser does not
need to load a large file containing formatted data and the browser does not
need to spend time determining how to lay out the many columns of data. Another
advantage is that the user can scroll through the data in its entirety. The
disadvantage of this option is that the user is not able to view superscripts,
subscripts, italics, etc. that can be viewed with formatted data.
Downloading Data
WWW browsers provide the capability for data to be downloaded and saved as a
local file. For downloading ASCII files, and/or for reading into
spreadsheets, we suggest the following procedure:
- On the Lines or Levels Form, go to the section "Output Options"
- Click the pulldown menu for "Format output" and choose "as ASCII
(TEXT),"
- Retrieve database output.
- Under "File," choose "Save as," assign the file a name,
and save it,
- In a text editor, remove any undesired headers from the saved ASCII
output file, and
- When reading the ASCII output file into spreadsheet softwave, specify the
delimiters as a black space and a pipe, i.e., ",|". This should
enable format-free reading.
Changing Fonts
Font size effects the amount of data that can be viewed per screen;
a smaller font size allows more data to fit on each screen.
Finding Specific Values in Output
WWW browsers provide the capability to find specific words/patterns in
a page of output displayed. For example, using an HTML page of output
for Lines Data or Levels Data, if the user searches for "5/2"
then the browser will scroll down to the line of data containing the value
specified and highlight the value.
Because of the way data is formatted,
care must be taken when searching for values. Note the following examples.
- To search for the configuration "2s22p2"
- for ASCII output: Search for the phrase "2s2.2p2 ." Note that periods are
inserted whenever necessary to avoid ambiguity due to the lack of superscripts.
Brackets enclose J values of the parent terms.
- HTML Table: Search for the phrase "2s2 2p2".
- To search for the term "3D" note that it is easier to specify a case sensitive search.
- To search for the term "2[5/2]:"
- ASCII output or HTML Table: Search for the phrase "2[5/2]."
- To search for the J value "5/2-3/2":
- ASCII output or HTML Table: Search for the phrase "5/2-3/2."
- To search for the energy level "60333.43:"
- ASCII output: Search for "60333.43".
- HTML Table: Search for "60 333.43"
- To search for the energy level "87 789.63":
- ASCII output: Search for "87789.63".
- HTML Table: Searching for the exact level is not possible. Try searching for either "87" "789"
or ".63". Note that searching for "87789" will not work.
To search for all energy levels greater than 87000, search for "87 ".
Printing Data
Many WWW browsers offer the capability to print directly from the browser. An
alternative is to download the data and then print the data from the local
computer.
The database provides an option which allows a user to choose the columns of
data to display. Suppressing specific columns of data might be helpful for
printing purposes. Specifying landscape orientation and reducing the font size
will simplify the task of printing a large amount of data.
The number of equivalent electrons (occupation number for a particular
subshell) is given as a full-size integer following the electron symbol
(e.g. 4d5 represents 4d5). The symbols for different
subshells not separated by parent terms or spaces are separated by periods
(e.g. 4f3.5d.6s2 represents 4f 35d6s2). The
multiplicity of a term is given immediately preceding the term symbol,
and an odd-parity term is indicated by a superscript asterisk following
the term symbol (e.g. 3H* represents
3H°). The parity of a level
having no term name is also indicated by the presence (odd parity) or absence
(even parity) of an asterisk in the "Term" column. The J value
of a level given with a configuration designation appears within "< >"
brackets following the term symbol (e.g. 2s2.2p4(3P<2>)3d
represents
2s22p4(3P2)3d
and (3p5(2P*<3/2>)5g represents
3p5(2P°3/2)5g).
The bibliography contains citations of all the compilations used in
the ASD database, and under each of these the original literature is
referenced. The bibliography is divided into three categories:
Energy Levels,
Transition Probabilities, and
Wavelengths.
When more than one element has been compiled in a given publication,
these elements are grouped together in a single hyperlink.
References to original publications cited in the compilations can
then be found via the "References to original literature" hyperlink
for each element.
To access references
select the "Bibliography" link on the ASD home page or
select the word "Bibliography" in the ASD menu bar.
For Lines Data
view the "TP Ref." and "Line Ref." columns of output
For Levels Data, check the "Bibliographic references" box on
on the Levels form and then click the hyperlink for "Energy Level
Bibliography" located at the top of the page of output. (Levels output)
Online: March 1999 - Last update: February 2005
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